feat: Add new services and interfaces for GRN, Purchase Return, Reason Code, Reorder, Stock, and Transfer functionalities

- Implemented IGrnService for managing goods receipts including retrieval, creation, and confirmation.
- Created IPurchaseReturnService for handling purchase return operations.
- Added IReasonCodeService for managing reason codes with listing and creation capabilities.
- Developed IReorderService for fetching reorder alerts and creating suggested requisitions.
- Introduced IStockMutator for applying stock changes and posting ledger entries.
- Established IStockService for stock inquiries, ledger retrieval, and valuation.
- Created ITransferService for managing inter-warehouse transfers including dispatch and receiving operations.
- Implemented PurchaseReturnService to handle purchase return logic and stock adjustments.
- Developed ReasonCodeService for listing and creating reason codes.
- Created ReorderService for fetching reorder alerts and generating requisitions.
- Implemented FifoCostingService for FIFO cost-layer management and ledger writing.
- Developed StockMutator for applying stock deltas and posting ledger entries.
- Created StockService for stock inquiries and ledger management.
- Implemented TransferService for managing inter-warehouse transfers with dispatch and receive functionalities.

Backend/ERPCore/Controllers/AuditLogsController.cs

@@ -0,0 +1,26 @@
+using ERPCore.Dtos.Audit;
+using ERPCore.Dtos.Common;
+using ERPCore.Services.Interfaces;
+using Microsoft.AspNetCore.Mvc;
+
+namespace ERPCore.Controllers;
+
+/// <summary>
+/// Read-only audit trail (FR-X-02; auditor role). Extends the documented §11 API —
+/// the audit trail is required (AR-01 compensating control) and read access is the
+/// only way to consume it.
+/// </summary>
+[Route("api/v1/audit-logs")]
+public sealed class AuditLogsController : ApiControllerBase
+{
+    private readonly IAuditService _audit;
+
+    public AuditLogsController(IAuditService audit) => _audit = audit;
+
+    [HttpGet]
+    [ProducesResponseType(typeof(PagedResponse<AuditLogDto>), StatusCodes.Status200OK)]
+    public async Task<ActionResult<PagedResponse<AuditLogDto>>> List(
+        [FromQuery] string? entityType, [FromQuery] long? entityId, [FromQuery] long? userId,
+        [FromQuery] DateOnly? from, [FromQuery] DateOnly? to, [FromQuery] PageQuery query, CancellationToken ct)
+        => Ok(await _audit.ListLogsAsync(entityType, entityId, userId, from, to, query, ct));
+}

Backend/ERPCore/Controllers/GrnsController.cs

@@ -0,0 +1,52 @@
+using ERPCore.Dtos.Grn;
+using ERPCore.Services.Interfaces;
+using Microsoft.AspNetCore.Mvc;
+
+namespace ERPCore.Controllers;
+
+/// <summary>Goods-receipt endpoints (docs/11 §4).</summary>
+[Route("api/v1/grns")]
+public sealed class GrnsController : ApiControllerBase
+{
+    private readonly IGrnService _grns;
+
+    public GrnsController(IGrnService grns) => _grns = grns;
+
+    [HttpGet("{grnId:long}")]
+    [ProducesResponseType(typeof(GrnDto), StatusCodes.Status200OK)]
+    [ProducesResponseType(StatusCodes.Status404NotFound)]
+    public async Task<ActionResult<GrnDto>> GetById(long grnId, CancellationToken ct)
+    {
+        var dto = await _grns.GetAsync(grnId, ct);
+        return dto is null ? NotFound() : Ok(dto);
+    }
+
+    /// <summary>Create a Draft GRN against a PO or direct. Cost is PO-derived for PO lines.</summary>
+    [HttpPost]
+    [ProducesResponseType(typeof(GrnDto), StatusCodes.Status201Created)]
+    [ProducesResponseType(StatusCodes.Status409Conflict)]
+    [ProducesResponseType(StatusCodes.Status422UnprocessableEntity)]
+    public async Task<ActionResult<GrnDto>> Create([FromBody] CreateGrnRequest request, CancellationToken ct)
+    {
+        var dto = await _grns.CreateAsync(request, ct);
+        return Created($"/api/v1/grns/{dto.GrnId}", dto);
+    }
+
+    /// <summary>Confirm: create FIFO layers + inbound ledger + update PO receipts (single UoW txn).</summary>
+    [HttpPost("{grnId:long}/confirm")]
+    [ProducesResponseType(typeof(GrnConfirmResultDto), StatusCodes.Status200OK)]
+    [ProducesResponseType(StatusCodes.Status404NotFound)]
+    [ProducesResponseType(StatusCodes.Status409Conflict)]
+    public async Task<ActionResult<GrnConfirmResultDto>> Confirm(
+        long grnId, [FromHeader(Name = "Idempotency-Key")] string? idempotencyKey, CancellationToken ct)
+        => Ok(await _grns.ConfirmAsync(grnId, idempotencyKey, ct));
+
+    /// <summary>Release or reject an inspection-hold line (FR-GRN-05).</summary>
+    [HttpPost("{grnId:long}/lines/{grnLineId:long}/release")]
+    [ProducesResponseType(typeof(ReleaseLineResultDto), StatusCodes.Status200OK)]
+    [ProducesResponseType(StatusCodes.Status404NotFound)]
+    [ProducesResponseType(StatusCodes.Status409Conflict)]
+    public async Task<ActionResult<ReleaseLineResultDto>> Release(
+        long grnId, long grnLineId, [FromBody] ReleaseLineRequest request, CancellationToken ct)
+        => Ok(await _grns.ReleaseLineAsync(grnId, grnLineId, request.Action, ct));
+}

Backend/ERPCore/Controllers/JournalEntriesController.cs

@@ -0,0 +1,24 @@
+using ERPCore.Dtos.Audit;
+using ERPCore.Dtos.Common;
+using ERPCore.Services.Interfaces;
+using Microsoft.AspNetCore.Mvc;
+
+namespace ERPCore.Controllers;
+
+/// <summary>
+/// Read-only GL-ready journal stubs (FR-STK-13; consumed by the Accounting phase).
+/// Data only — no posting in Phase 1.
+/// </summary>
+[Route("api/v1/journal-entries")]
+public sealed class JournalEntriesController : ApiControllerBase
+{
+    private readonly IAuditService _audit;
+
+    public JournalEntriesController(IAuditService audit) => _audit = audit;
+
+    [HttpGet]
+    [ProducesResponseType(typeof(PagedResponse<JournalEntryStubDto>), StatusCodes.Status200OK)]
+    public async Task<ActionResult<PagedResponse<JournalEntryStubDto>>> List(
+        [FromQuery] string? sourceDocType, [FromQuery] long? sourceDocId, [FromQuery] PageQuery query, CancellationToken ct)
+        => Ok(await _audit.ListJournalAsync(sourceDocType, sourceDocId, query, ct));
+}

Backend/ERPCore/Controllers/PurchaseReturnsController.cs

@@ -0,0 +1,26 @@
+using ERPCore.Dtos.Procurement;
+using ERPCore.Services.Interfaces;
+using Microsoft.AspNetCore.Mvc;
+
+namespace ERPCore.Controllers;
+
+/// <summary>Purchase-return endpoints (docs/11 §3.4).</summary>
+[Route("api/v1/purchase-returns")]
+public sealed class PurchaseReturnsController : ApiControllerBase
+{
+    private readonly IPurchaseReturnService _returns;
+
+    public PurchaseReturnsController(IPurchaseReturnService returns) => _returns = returns;
+
+    /// <summary>Create + auto-post a return (outbound movement). 409 if return exceeds available stock.</summary>
+    [HttpPost]
+    [ProducesResponseType(typeof(PurchaseReturnDto), StatusCodes.Status201Created)]
+    [ProducesResponseType(StatusCodes.Status400BadRequest)]
+    [ProducesResponseType(StatusCodes.Status409Conflict)]
+    [ProducesResponseType(StatusCodes.Status422UnprocessableEntity)]
+    public async Task<ActionResult<PurchaseReturnDto>> Create([FromBody] CreatePurchaseReturnRequest request, CancellationToken ct)
+    {
+        var dto = await _returns.CreateAsync(request, ct);
+        return Created($"/api/v1/purchase-returns/{dto.ReturnId}", dto);
+    }
+}

Backend/ERPCore/Controllers/ReasonCodesController.cs

@@ -0,0 +1,31 @@
+using ERPCore.Domain.Enums;
+using ERPCore.Dtos.Common;
+using ERPCore.Dtos.Reference;
+using ERPCore.Services.Interfaces;
+using Microsoft.AspNetCore.Mvc;
+
+namespace ERPCore.Controllers;
+
+/// <summary>Reason-code reference endpoints (docs/11 §6).</summary>
+[Route("api/v1/reason-codes")]
+public sealed class ReasonCodesController : ApiControllerBase
+{
+    private readonly IReasonCodeService _codes;
+
+    public ReasonCodesController(IReasonCodeService codes) => _codes = codes;
+
+    [HttpGet]
+    [ProducesResponseType(typeof(PagedResponse<ReasonCodeDto>), StatusCodes.Status200OK)]
+    public async Task<ActionResult<PagedResponse<ReasonCodeDto>>> List(
+        [FromQuery] ReasonContext? context, [FromQuery] PageQuery query, CancellationToken ct)
+        => Ok(await _codes.ListAsync(context, query, ct));
+
+    [HttpPost]
+    [ProducesResponseType(typeof(ReasonCodeDto), StatusCodes.Status201Created)]
+    [ProducesResponseType(StatusCodes.Status409Conflict)]
+    public async Task<ActionResult<ReasonCodeDto>> Create([FromBody] CreateReasonCodeRequest request, CancellationToken ct)
+    {
+        var dto = await _codes.CreateAsync(request, ct);
+        return Created($"/api/v1/reason-codes/{dto.ReasonCodeId}", dto);
+    }
+}

Backend/ERPCore/Controllers/StockAdjustmentsController.cs

@@ -0,0 +1,26 @@
+using ERPCore.Dtos.Stock;
+using ERPCore.Services.Interfaces;
+using Microsoft.AspNetCore.Mvc;
+
+namespace ERPCore.Controllers;
+
+/// <summary>Stock-adjustment endpoints (docs/11 §5.5).</summary>
+[Route("api/v1/stock-adjustments")]
+public sealed class StockAdjustmentsController : ApiControllerBase
+{
+    private readonly IAdjustmentService _adjustments;
+
+    public StockAdjustmentsController(IAdjustmentService adjustments) => _adjustments = adjustments;
+
+    /// <summary>Create + auto-post an adjustment (mandatory reason code; decrease FIFO-consumes).</summary>
+    [HttpPost]
+    [ProducesResponseType(typeof(AdjustmentDto), StatusCodes.Status201Created)]
+    [ProducesResponseType(StatusCodes.Status400BadRequest)]
+    [ProducesResponseType(StatusCodes.Status409Conflict)]
+    [ProducesResponseType(StatusCodes.Status422UnprocessableEntity)]
+    public async Task<ActionResult<AdjustmentDto>> Create([FromBody] CreateAdjustmentRequest request, CancellationToken ct)
+    {
+        var dto = await _adjustments.CreateAsync(request, ct);
+        return Created($"/api/v1/stock-adjustments/{dto.AdjustmentId}", dto);
+    }
+}

Backend/ERPCore/Controllers/StockController.cs

@@ -0,0 +1,56 @@
+using ERPCore.Dtos.Common;
+using ERPCore.Dtos.Procurement;
+using ERPCore.Dtos.Stock;
+using ERPCore.Services.Interfaces;
+using Microsoft.AspNetCore.Mvc;
+
+namespace ERPCore.Controllers;
+
+/// <summary>Stock enquiry, ledger, valuation and reorder-alert endpoints (docs/11 §5.1–5.3, §5.7).</summary>
+[Route("api/v1/stock")]
+public sealed class StockController : ApiControllerBase
+{
+    private readonly IStockService _stock;
+    private readonly IReorderService _reorder;
+
+    public StockController(IStockService stock, IReorderService reorder)
+    {
+        _stock = stock;
+        _reorder = reorder;
+    }
+
+    [HttpGet("on-hand")]
+    [ProducesResponseType(typeof(StockOnHandDto), StatusCodes.Status200OK)]
+    public async Task<ActionResult<StockOnHandDto>> OnHand([FromQuery] long itemId, [FromQuery] long warehouseId, CancellationToken ct)
+        => Ok(await _stock.GetOnHandAsync(itemId, warehouseId, ct));
+
+    [HttpGet("ledger")]
+    [ProducesResponseType(typeof(PagedResponse<StockLedgerRowDto>), StatusCodes.Status200OK)]
+    public async Task<ActionResult<PagedResponse<StockLedgerRowDto>>> Ledger(
+        [FromQuery] long? itemId, [FromQuery] long? warehouseId,
+        [FromQuery] DateOnly? from, [FromQuery] DateOnly? to, [FromQuery] PageQuery query, CancellationToken ct)
+        => Ok(await _stock.GetLedgerAsync(itemId, warehouseId, from, to, query, ct));
+
+    [HttpGet("valuation")]
+    [ProducesResponseType(typeof(StockValuationDto), StatusCodes.Status200OK)]
+    public async Task<ActionResult<StockValuationDto>> Valuation([FromQuery] long itemId, [FromQuery] long warehouseId, CancellationToken ct)
+        => Ok(await _stock.GetValuationAsync(itemId, warehouseId, ct));
+
+    /// <summary>Items at/below their reorder point (FR-STK-10), computed on read.</summary>
+    [HttpGet("reorder-alerts")]
+    [ProducesResponseType(typeof(PagedResponse<ReorderAlertDto>), StatusCodes.Status200OK)]
+    public async Task<ActionResult<PagedResponse<ReorderAlertDto>>> ReorderAlerts(
+        [FromQuery] long? warehouseId, [FromQuery] PageQuery query, CancellationToken ct)
+        => Ok(await _reorder.GetAlertsAsync(warehouseId, query, ct));
+
+    /// <summary>Create a draft requisition for an item's suggested reorder quantity.</summary>
+    [HttpPost("reorder-alerts/{itemId:long}/requisition")]
+    [ProducesResponseType(typeof(RequisitionDto), StatusCodes.Status201Created)]
+    [ProducesResponseType(StatusCodes.Status422UnprocessableEntity)]
+    public async Task<ActionResult<RequisitionDto>> SuggestRequisition(
+        long itemId, [FromQuery] long warehouseId, CancellationToken ct)
+    {
+        var dto = await _reorder.CreateSuggestedRequisitionAsync(itemId, warehouseId, ct);
+        return Created($"/api/v1/requisitions/{dto.RequisitionId}", dto);
+    }
+}

Backend/ERPCore/Controllers/StockCountsController.cs

@@ -0,0 +1,49 @@
+using ERPCore.Dtos.Stock;
+using ERPCore.Services.Interfaces;
+using Microsoft.AspNetCore.Mvc;
+
+namespace ERPCore.Controllers;
+
+/// <summary>Stock-count endpoints (docs/11 §5.6).</summary>
+[Route("api/v1/stock-counts")]
+public sealed class StockCountsController : ApiControllerBase
+{
+    private readonly ICountService _counts;
+
+    public StockCountsController(ICountService counts) => _counts = counts;
+
+    [HttpGet("{countId:long}")]
+    [ProducesResponseType(typeof(CountDto), StatusCodes.Status200OK)]
+    [ProducesResponseType(StatusCodes.Status404NotFound)]
+    public async Task<ActionResult<CountDto>> GetById(long countId, CancellationToken ct)
+    {
+        var dto = await _counts.GetAsync(countId, ct);
+        return dto is null ? NotFound() : Ok(dto);
+    }
+
+    /// <summary>Create a count with system quantities snapshotted (immutable).</summary>
+    [HttpPost]
+    [ProducesResponseType(typeof(CountDto), StatusCodes.Status201Created)]
+    [ProducesResponseType(StatusCodes.Status422UnprocessableEntity)]
+    public async Task<ActionResult<CountDto>> Create([FromBody] CreateCountRequest request, CancellationToken ct)
+    {
+        var dto = await _counts.CreateAsync(request, ct);
+        return Created($"/api/v1/stock-counts/{dto.CountId}", dto);
+    }
+
+    /// <summary>Enter counted quantities; variance = counted − system.</summary>
+    [HttpPut("{countId:long}/counts")]
+    [ProducesResponseType(typeof(CountDto), StatusCodes.Status200OK)]
+    [ProducesResponseType(StatusCodes.Status404NotFound)]
+    [ProducesResponseType(StatusCodes.Status409Conflict)]
+    public async Task<ActionResult<CountDto>> EnterCounts(long countId, [FromBody] EnterCountsRequest request, CancellationToken ct)
+        => Ok(await _counts.EnterCountsAsync(countId, request, ct));
+
+    /// <summary>Post: emit a variance adjustment and close the count.</summary>
+    [HttpPost("{countId:long}/post")]
+    [ProducesResponseType(typeof(CountPostResultDto), StatusCodes.Status200OK)]
+    [ProducesResponseType(StatusCodes.Status404NotFound)]
+    [ProducesResponseType(StatusCodes.Status409Conflict)]
+    public async Task<ActionResult<CountPostResultDto>> Post(long countId, CancellationToken ct)
+        => Ok(await _counts.PostAsync(countId, ct));
+}

Backend/ERPCore/Controllers/StockTransfersController.cs

@@ -0,0 +1,49 @@
+using ERPCore.Dtos.Stock;
+using ERPCore.Services.Interfaces;
+using Microsoft.AspNetCore.Mvc;
+
+namespace ERPCore.Controllers;
+
+/// <summary>Stock-transfer endpoints (docs/11 §5.4).</summary>
+[Route("api/v1/stock-transfers")]
+public sealed class StockTransfersController : ApiControllerBase
+{
+    private readonly ITransferService _transfers;
+
+    public StockTransfersController(ITransferService transfers) => _transfers = transfers;
+
+    [HttpGet("{transferId:long}")]
+    [ProducesResponseType(typeof(TransferDto), StatusCodes.Status200OK)]
+    [ProducesResponseType(StatusCodes.Status404NotFound)]
+    public async Task<ActionResult<TransferDto>> GetById(long transferId, CancellationToken ct)
+    {
+        var dto = await _transfers.GetAsync(transferId, ct);
+        return dto is null ? NotFound() : Ok(dto);
+    }
+
+    [HttpPost]
+    [ProducesResponseType(typeof(TransferDto), StatusCodes.Status201Created)]
+    [ProducesResponseType(StatusCodes.Status422UnprocessableEntity)]
+    public async Task<ActionResult<TransferDto>> Create([FromBody] CreateTransferRequest request, CancellationToken ct)
+    {
+        var dto = await _transfers.CreateAsync(request, ct);
+        return Created($"/api/v1/stock-transfers/{dto.TransferId}", dto);
+    }
+
+    /// <summary>Dispatch: consume source FIFO layers into in-transit. 409 STOCK_NEGATIVE_BLOCKED if short.</summary>
+    [HttpPost("{transferId:long}/dispatch")]
+    [ProducesResponseType(typeof(DispatchResultDto), StatusCodes.Status200OK)]
+    [ProducesResponseType(StatusCodes.Status404NotFound)]
+    [ProducesResponseType(StatusCodes.Status409Conflict)]
+    public async Task<ActionResult<DispatchResultDto>> Dispatch(long transferId, CancellationToken ct)
+        => Ok(await _transfers.DispatchAsync(transferId, ct));
+
+    /// <summary>Receive: create the destination layer at the inherited cost (cost-preserving).</summary>
+    [HttpPost("{transferId:long}/receive")]
+    [ProducesResponseType(typeof(ReceiveResultDto), StatusCodes.Status200OK)]
+    [ProducesResponseType(StatusCodes.Status404NotFound)]
+    [ProducesResponseType(StatusCodes.Status409Conflict)]
+    [ProducesResponseType(StatusCodes.Status422UnprocessableEntity)]
+    public async Task<ActionResult<ReceiveResultDto>> Receive(long transferId, [FromBody] ReceiveTransferRequest request, CancellationToken ct)
+        => Ok(await _transfers.ReceiveAsync(transferId, request, ct));
+}

Backend/ERPCore/Domain/Entities/AuditLog.cs

@@ -0,0 +1,23 @@
+using ERPCore.Domain.Enums;
+
+namespace ERPCore.Domain.Entities;
+
+/// <summary>
+/// Immutable audit trail entry (FR-X-02) — the compensating control for the deferred
+/// RBAC (02-SECURITY AR-01/B.3). One row per create/update/delete of an audited
+/// entity, capturing who / when / what changed (old→new in <see cref="ChangeSet"/>).
+/// Written automatically by <c>ErpDbContext.SaveChangesAsync</c>. Append-only at the
+/// app level; DB-role revocation of UPDATE/DELETE is deferred hardening (B.3).
+/// Model: docs/10 Part C.7.
+/// </summary>
+public class AuditLog
+{
+    public long AuditId { get; set; }
+    public long UserId { get; set; }
+    public string EntityType { get; set; } = string.Empty;
+    public long EntityId { get; set; }
+    public AuditAction Action { get; set; }
+    /// <summary>JSON change set: field→value (create/delete) or field→{old,new} (update).</summary>
+    public string ChangeSet { get; set; } = "{}";
+    public DateTime CreatedAt { get; set; }
+}

Backend/ERPCore/Domain/Entities/Batch.cs

@@ -0,0 +1,16 @@
+namespace ERPCore.Domain.Entities;
+
+/// <summary>
+/// Batch/lot for a batch-tracked item (FR-GRN-04, FR-WH-03). Expiry drives FEFO
+/// picking of perishables. Model: docs/10 Part C.4.
+/// </summary>
+public class Batch
+{
+    public long BatchId { get; set; }
+
+    public long ItemId { get; set; }
+    public Item? Item { get; set; }
+
+    public string BatchNo { get; set; } = string.Empty;
+    public DateOnly? ExpiryDate { get; set; }
+}

Backend/ERPCore/Domain/Entities/Grn.cs

@@ -0,0 +1,37 @@
+using ERPCore.Domain.Enums;
+
+namespace ERPCore.Domain.Entities;
+
+/// <summary>
+/// Goods Receipt Note header (FR-GRN-01/02). Raised against a PO or direct
+/// (<see cref="PoId"/> null). On confirm each line creates a FIFO layer and posts
+/// an inbound ledger entry. Mutable aggregate with an <see cref="RowVersion"/>
+/// concurrency token (docs/10 C.10). Model: docs/10 Part C.3.
+/// </summary>
+public class Grn
+{
+    public long GrnId { get; set; }
+    public string DocNo { get; set; } = string.Empty;
+
+    public long? PoId { get; set; }
+    public PurchaseOrder? PurchaseOrder { get; set; }
+
+    public long VendorId { get; set; }
+    public Vendor? Vendor { get; set; }
+
+    public long WarehouseId { get; set; }
+    public Warehouse? Warehouse { get; set; }
+
+    public GrnStatus Status { get; set; } = GrnStatus.Draft;
+
+    public long CreatedBy { get; set; }
+    public User? Creator { get; set; }
+
+    public DateTime CreatedAt { get; set; }
+    public DateTime? PostedAt { get; set; }
+
+    /// <summary>PostgreSQL xmin-backed optimistic concurrency token.</summary>
+    public uint RowVersion { get; set; }
+
+    public ICollection<GrnLine> Lines { get; set; } = new List<GrnLine>();
+}

Backend/ERPCore/Domain/Entities/GrnLine.cs

@@ -0,0 +1,37 @@
+using ERPCore.Domain.Enums;
+
+namespace ERPCore.Domain.Entities;
+
+/// <summary>
+/// GRN line (FR-GRN-04..08). <see cref="UnitCost"/> is the PO-derived cost for
+/// PO-based receipts (client cost ignored — 02-SECURITY C.3) or the entered cost
+/// for direct receipts. <see cref="ReceivedValue"/> = qty × unitCost.
+/// <see cref="HoldStatus"/> gates issuability. Model: docs/10 Part C.3.
+/// </summary>
+public class GrnLine
+{
+    public long GrnLineId { get; set; }
+
+    public long GrnId { get; set; }
+    public Grn? Grn { get; set; }
+
+    public long? PoLineId { get; set; }
+    public PoLine? PoLine { get; set; }
+
+    public long ItemId { get; set; }
+    public Item? Item { get; set; }
+
+    public long UomId { get; set; }
+    public Uom? Uom { get; set; }
+
+    public long? BinId { get; set; }
+    public Bin? Bin { get; set; }
+
+    public long? BatchId { get; set; }
+    public Batch? Batch { get; set; }
+
+    public decimal Qty { get; set; }
+    public decimal UnitCost { get; set; }
+    public decimal ReceivedValue { get; set; }
+    public HoldStatus HoldStatus { get; set; } = HoldStatus.Available;
+}

Backend/ERPCore/Domain/Entities/JournalEntryStub.cs

@@ -0,0 +1,18 @@
+namespace ERPCore.Domain.Entities;
+
+/// <summary>
+/// GL-ready journal entry emitted per stock movement (FR-STK-13) — data only, no
+/// posting in Phase 1 (the Accounting module consumes these later). One row per
+/// ledger entry, referencing the same source document polymorphically. Account
+/// codes are Phase-1 placeholders until a chart of accounts exists.
+/// Model: docs/10 Part C.7.
+/// </summary>
+public class JournalEntryStub
+{
+    public long JournalId { get; set; }
+    public string SourceDocType { get; set; } = string.Empty;
+    public long SourceDocId { get; set; }
+    public string DebitAccount { get; set; } = string.Empty;
+    public string CreditAccount { get; set; } = string.Empty;
+    public decimal Amount { get; set; }
+}

Backend/ERPCore/Domain/Entities/PurchaseReturn.cs

@@ -0,0 +1,32 @@
+using ERPCore.Domain.Enums;
+
+namespace ERPCore.Domain.Entities;
+
+/// <summary>
+/// Purchase return header (FR-PROC-08) — returns received goods to a vendor,
+/// generating an outbound stock movement. Auto-posts with a mandatory reason code.
+/// Model: docs/10 Part C.2.
+/// </summary>
+public class PurchaseReturn
+{
+    public long ReturnId { get; set; }
+    public string DocNo { get; set; } = string.Empty;
+
+    public long VendorId { get; set; }
+    public Vendor? Vendor { get; set; }
+
+    public long WarehouseId { get; set; }
+    public Warehouse? Warehouse { get; set; }
+
+    public long ReasonCodeId { get; set; }
+    public ReasonCode? ReasonCode { get; set; }
+
+    public ReturnStatus Status { get; set; } = ReturnStatus.Posted;
+
+    public long CreatedBy { get; set; }
+    public User? Creator { get; set; }
+
+    public DateTime CreatedAt { get; set; }
+
+    public ICollection<PurchaseReturnLine> Lines { get; set; } = new List<PurchaseReturnLine>();
+}

Backend/ERPCore/Domain/Entities/PurchaseReturnLine.cs

@@ -0,0 +1,21 @@
+namespace ERPCore.Domain.Entities;
+
+/// <summary>
+/// Purchase-return line (FR-PROC-08) referencing the original GRN line for
+/// traceability. <see cref="Qty"/> is in base UOM. Model: docs/10 Part C.2.
+/// </summary>
+public class PurchaseReturnLine
+{
+    public long ReturnLineId { get; set; }
+
+    public long ReturnId { get; set; }
+    public PurchaseReturn? Return { get; set; }
+
+    public long? GrnLineId { get; set; }
+    public GrnLine? GrnLine { get; set; }
+
+    public long ItemId { get; set; }
+    public Item? Item { get; set; }
+
+    public decimal Qty { get; set; }
+}

Backend/ERPCore/Domain/Entities/ReasonCode.cs

@@ -0,0 +1,15 @@
+using ERPCore.Domain.Enums;
+
+namespace ERPCore.Domain.Entities;
+
+/// <summary>
+/// Configurable reason code for adjustments, returns and count variances
+/// (FR-X-04). Model: docs/10 Part C.7.
+/// </summary>
+public class ReasonCode
+{
+    public long ReasonCodeId { get; set; }
+    public string Code { get; set; } = string.Empty;
+    public string Description { get; set; } = string.Empty;
+    public ReasonContext Context { get; set; }
+}

Backend/ERPCore/Domain/Entities/Serial.cs

@@ -0,0 +1,16 @@
+namespace ERPCore.Domain.Entities;
+
+/// <summary>
+/// Serial number for a serial-tracked item across its lifecycle (FR-WH-04).
+/// Model: docs/10 Part C.4.
+/// </summary>
+public class Serial
+{
+    public long SerialId { get; set; }
+
+    public long ItemId { get; set; }
+    public Item? Item { get; set; }
+
+    public string SerialNo { get; set; } = string.Empty;
+    public string Status { get; set; } = "InStock";
+}

Backend/ERPCore/Domain/Entities/StockAdjustment.cs

@@ -0,0 +1,31 @@
+using ERPCore.Domain.Enums;
+
+namespace ERPCore.Domain.Entities;
+
+/// <summary>
+/// Stock adjustment header (FR-STK-07) — the highest-risk feature in the phase
+/// (02-SECURITY C.5). Auto-posts in Phase 1 with a mandatory reason code and user
+/// stamp. Mutable aggregate with an <see cref="RowVersion"/> token (docs/10 C.10).
+/// Model: docs/10 Part C.6.
+/// </summary>
+public class StockAdjustment
+{
+    public long AdjustmentId { get; set; }
+    public string DocNo { get; set; } = string.Empty;
+
+    public long WarehouseId { get; set; }
+    public Warehouse? Warehouse { get; set; }
+
+    public long ReasonCodeId { get; set; }
+    public ReasonCode? ReasonCode { get; set; }
+
+    public AdjustmentStatus Status { get; set; } = AdjustmentStatus.Posted;
+
+    public long CreatedBy { get; set; }
+    public User? Creator { get; set; }
+
+    public DateTime CreatedAt { get; set; }
+    public uint RowVersion { get; set; }
+
+    public ICollection<StockAdjustmentLine> Lines { get; set; } = new List<StockAdjustmentLine>();
+}

Backend/ERPCore/Domain/Entities/StockAdjustmentLine.cs

@@ -0,0 +1,23 @@
+namespace ERPCore.Domain.Entities;
+
+/// <summary>
+/// Adjustment line (FR-STK-07). <see cref="QtyDelta"/> is a signed base-UOM
+/// quantity: negative consumes FIFO layers, positive creates a layer at last cost.
+/// Model: docs/10 Part C.6.
+/// </summary>
+public class StockAdjustmentLine
+{
+    public long AdjLineId { get; set; }
+
+    public long AdjustmentId { get; set; }
+    public StockAdjustment? Adjustment { get; set; }
+
+    public long ItemId { get; set; }
+    public Item? Item { get; set; }
+
+    public long? BinId { get; set; }
+    public long? BatchId { get; set; }
+    public long? SerialId { get; set; }
+
+    public decimal QtyDelta { get; set; }
+}

Backend/ERPCore/Domain/Entities/StockCount.cs

@@ -0,0 +1,29 @@
+using ERPCore.Domain.Enums;
+
+namespace ERPCore.Domain.Entities;
+
+/// <summary>
+/// Cycle/full physical count header (FR-STK-08). System quantities are snapshotted
+/// at creation and are immutable once opened (02-SECURITY C.7); posting emits a
+/// variance adjustment. Mutable aggregate with an <see cref="RowVersion"/> token.
+/// Model: docs/10 Part C.6.
+/// </summary>
+public class StockCount
+{
+    public long CountId { get; set; }
+    public string DocNo { get; set; } = string.Empty;
+
+    public long WarehouseId { get; set; }
+    public Warehouse? Warehouse { get; set; }
+
+    public CountType CountType { get; set; }
+    public CountStatus Status { get; set; } = CountStatus.Draft;
+
+    public long CreatedBy { get; set; }
+    public User? Creator { get; set; }
+
+    public DateTime CreatedAt { get; set; }
+    public uint RowVersion { get; set; }
+
+    public ICollection<StockCountLine> Lines { get; set; } = new List<StockCountLine>();
+}

Backend/ERPCore/Domain/Entities/StockCountLine.cs

@@ -0,0 +1,22 @@
+namespace ERPCore.Domain.Entities;
+
+/// <summary>
+/// Count line (FR-STK-08). <see cref="SystemQty"/> is the immutable snapshot;
+/// <see cref="Variance"/> = counted − system (in base UOM). Model: docs/10 Part C.6.
+/// </summary>
+public class StockCountLine
+{
+    public long CountLineId { get; set; }
+
+    public long CountId { get; set; }
+    public StockCount? Count { get; set; }
+
+    public long ItemId { get; set; }
+    public Item? Item { get; set; }
+
+    public long? BinId { get; set; }
+
+    public decimal SystemQty { get; set; }
+    public decimal? CountedQty { get; set; }
+    public decimal? Variance { get; set; }
+}

Backend/ERPCore/Domain/Entities/StockLayer.cs

@@ -0,0 +1,33 @@
+namespace ERPCore.Domain.Entities;
+
+/// <summary>
+/// FIFO cost layer — a quantity received at a specific unit cost, consumed
+/// oldest-first (FR-STK-02). Keyed per item **per warehouse**; quantities and
+/// <see cref="UnitCost"/> are in the item's base UOM. Answers valuation
+/// ("what's on hand and at what cost"). Model: docs/10 Part C.5.
+/// </summary>
+public class StockLayer
+{
+    public long LayerId { get; set; }
+
+    public long ItemId { get; set; }
+    public Item? Item { get; set; }
+
+    public long WarehouseId { get; set; }
+    public Warehouse? Warehouse { get; set; }
+
+    public long? BatchId { get; set; }
+    public Batch? Batch { get; set; }
+
+    public long? SerialId { get; set; }
+    public Serial? Serial { get; set; }
+
+    /// <summary>Originating GRN line — carries the inspection hold status for this stock.</summary>
+    public long? GrnLineId { get; set; }
+    public GrnLine? GrnLine { get; set; }
+
+    public decimal QtyReceived { get; set; }
+    public decimal QtyRemaining { get; set; }
+    public decimal UnitCost { get; set; }
+    public DateTime ReceiptDate { get; set; }
+}

Backend/ERPCore/Domain/Entities/StockLedger.cs

@@ -0,0 +1,32 @@
+using ERPCore.Domain.Enums;
+
+namespace ERPCore.Domain.Entities;
+
+/// <summary>
+/// Immutable, append-only stock ledger (FR-STK-01, FR-X-05). One row per costed
+/// movement; answers history ("what moved, when, by whom"). The originating
+/// document is referenced polymorphically via
+/// <see cref="SourceDocType"/>/<see cref="SourceDocId"/> (no hard FK per type) so
+/// new transaction types write here without a schema change. Model: docs/10 Part C.5.
+/// </summary>
+public class StockLedger
+{
+    public long LedgerId { get; set; }
+
+    public long ItemId { get; set; }
+    public long WarehouseId { get; set; }
+    public long? BinId { get; set; }
+    public long? BatchId { get; set; }
+    public long? SerialId { get; set; }
+    public long UserId { get; set; }
+
+    public Direction Direction { get; set; }
+    public decimal QtyBase { get; set; }
+    public decimal UnitCost { get; set; }
+    public decimal Value { get; set; }
+    public decimal RunningBalance { get; set; }
+
+    public string SourceDocType { get; set; } = string.Empty;
+    public long SourceDocId { get; set; }
+    public DateTime CreatedAt { get; set; }
+}

Backend/ERPCore/Domain/Entities/StockTransfer.cs

@@ -0,0 +1,31 @@
+using ERPCore.Domain.Enums;
+
+namespace ERPCore.Domain.Entities;
+
+/// <summary>
+/// Inter-warehouse stock transfer header (FR-STK-05/06). Dispatch consumes source
+/// FIFO layers into in-transit; receive creates the destination layer at the
+/// inherited cost (cost-preserving). Mutable aggregate with an
+/// <see cref="RowVersion"/> token (docs/10 C.10). Model: docs/10 Part C.6.
+/// </summary>
+public class StockTransfer
+{
+    public long TransferId { get; set; }
+    public string DocNo { get; set; } = string.Empty;
+
+    public long SrcWarehouseId { get; set; }
+    public Warehouse? SrcWarehouse { get; set; }
+
+    public long DestWarehouseId { get; set; }
+    public Warehouse? DestWarehouse { get; set; }
+
+    public TransferStatus Status { get; set; } = TransferStatus.Draft;
+
+    public long CreatedBy { get; set; }
+    public User? Creator { get; set; }
+
+    public DateTime CreatedAt { get; set; }
+    public uint RowVersion { get; set; }
+
+    public ICollection<StockTransferLine> Lines { get; set; } = new List<StockTransferLine>();
+}

Backend/ERPCore/Domain/Entities/StockTransferLine.cs

@@ -0,0 +1,35 @@
+namespace ERPCore.Domain.Entities;
+
+/// <summary>
+/// Transfer line (FR-STK-05/06). <see cref="Qty"/> is in base UOM.
+/// <para>
+/// Deviation note: <see cref="UnitCost"/> and <see cref="QtyReceived"/> extend
+/// docs/10 Part C.6's <c>STOCK_TRANSFER_LINE</c> to make the transfer
+/// cost-preserving: at dispatch the value-weighted cost of the consumed source
+/// layers is stored here, and receive recreates the destination layer at that cost
+/// (supports partial receive via <see cref="QtyReceived"/>).
+/// </para>
+/// </summary>
+public class StockTransferLine
+{
+    public long TransferLineId { get; set; }
+
+    public long TransferId { get; set; }
+    public StockTransfer? Transfer { get; set; }
+
+    public long ItemId { get; set; }
+    public Item? Item { get; set; }
+
+    public long? SrcBinId { get; set; }
+    public long? DestBinId { get; set; }
+    public long? BatchId { get; set; }
+    public long? SerialId { get; set; }
+
+    public decimal Qty { get; set; }
+
+    /// <summary>Value-weighted unit cost of the consumed source layers (set at dispatch).</summary>
+    public decimal? UnitCost { get; set; }
+
+    /// <summary>Quantity already received at the destination (partial-receive support).</summary>
+    public decimal QtyReceived { get; set; }
+}

Backend/ERPCore/Domain/Enums/AdjustmentStatus.cs

@@ -0,0 +1,13 @@
+namespace ERPCore.Domain.Enums;
+
+/// <summary>
+/// Stock-adjustment lifecycle (docs/10 §B.8.1). Phase 1 auto-posts, so
+/// <see cref="PendingApproval"/> is reserved for the future threshold-approval
+/// workflow (FR-STK-07). Stored as a string.
+/// </summary>
+public enum AdjustmentStatus
+{
+    Draft,
+    PendingApproval,
+    Posted
+}

Backend/ERPCore/Domain/Enums/AuditAction.cs

@@ -0,0 +1,9 @@
+namespace ERPCore.Domain.Enums;
+
+/// <summary>Kind of mutation recorded in the audit trail (FR-X-02). Stored as a string.</summary>
+public enum AuditAction
+{
+    Create,
+    Update,
+    Delete
+}

Backend/ERPCore/Domain/Enums/CountStatus.cs

@@ -0,0 +1,9 @@
+namespace ERPCore.Domain.Enums;
+
+/// <summary>Stock-count lifecycle (docs/11 §8; docs/10 §B.8.1). Stored as a string.</summary>
+public enum CountStatus
+{
+    Draft,
+    Counted,
+    Posted
+}

Backend/ERPCore/Domain/Enums/CountType.cs

@@ -0,0 +1,8 @@
+namespace ERPCore.Domain.Enums;
+
+/// <summary>Physical-count scope (docs/11 §8; FR-STK-08). Stored as a string.</summary>
+public enum CountType
+{
+    Cycle,
+    Full
+}

Backend/ERPCore/Domain/Enums/Direction.cs

@@ -0,0 +1,8 @@
+namespace ERPCore.Domain.Enums;
+
+/// <summary>Stock-ledger movement direction (docs/11 §8). Stored as a string.</summary>
+public enum Direction
+{
+    In,
+    Out
+}

Backend/ERPCore/Domain/Enums/GrnStatus.cs

@@ -0,0 +1,9 @@
+namespace ERPCore.Domain.Enums;
+
+/// <summary>Goods-receipt-note lifecycle (docs/11 §8; docs/10 §B.8.1). Stored as a string.</summary>
+public enum GrnStatus
+{
+    Draft,
+    Confirmed,
+    Closed
+}

Backend/ERPCore/Domain/Enums/HoldStatus.cs

@@ -0,0 +1,12 @@
+namespace ERPCore.Domain.Enums;
+
+/// <summary>
+/// Inspection-hold state of received stock (docs/11 §8; FR-GRN-05). <see cref="OnHold"/>
+/// stock is on-hand but not issuable until released (FR-WH-07). Stored as a string.
+/// </summary>
+public enum HoldStatus
+{
+    Available,
+    OnHold,
+    Rejected
+}

Backend/ERPCore/Domain/Enums/ReasonContext.cs

@@ -0,0 +1,9 @@
+namespace ERPCore.Domain.Enums;
+
+/// <summary>Where a reason code applies (FR-X-04; docs/10 §B.8.3). Stored as a string.</summary>
+public enum ReasonContext
+{
+    Adjustment,
+    Return,
+    Count
+}

Backend/ERPCore/Domain/Enums/ReturnStatus.cs

@@ -0,0 +1,8 @@
+namespace ERPCore.Domain.Enums;
+
+/// <summary>Purchase-return lifecycle (docs/11 §3.4). Auto-posts in Phase 1. Stored as a string.</summary>
+public enum ReturnStatus
+{
+    Draft,
+    Posted
+}

Backend/ERPCore/Domain/Enums/TransferStatus.cs

@@ -0,0 +1,10 @@
+namespace ERPCore.Domain.Enums;
+
+/// <summary>Stock-transfer lifecycle (docs/11 §8; docs/10 §B.8.1). Stored as a string.</summary>
+public enum TransferStatus
+{
+    Draft,
+    InTransit,
+    Received,
+    Closed
+}

Backend/ERPCore/Dtos/Audit/AuditDtos.cs

@@ -0,0 +1,12 @@
+using System.Text.Json;
+using ERPCore.Domain.Enums;
+
+namespace ERPCore.Dtos.Audit;
+
+/// <summary>An audit-trail entry (FR-X-02). <c>ChangeSet</c> is the stored JSON, inlined.</summary>
+public sealed record AuditLogDto(
+    long AuditId, long UserId, string EntityType, long EntityId, AuditAction Action, JsonElement ChangeSet, DateTime CreatedAt);
+
+/// <summary>A GL-ready journal stub emitted per stock movement (FR-STK-13).</summary>
+public sealed record JournalEntryStubDto(
+    long JournalId, string SourceDocType, long SourceDocId, string DebitAccount, string CreditAccount, decimal Amount);

Backend/ERPCore/Dtos/Grn/GrnDtos.cs

@@ -0,0 +1,63 @@
+using System.ComponentModel.DataAnnotations;
+using ERPCore.Domain.Enums;
+
+namespace ERPCore.Dtos.Grn;
+
+// Responses (docs/11 §4) --------------------------------------------------------
+
+public sealed record GrnLineDto(
+    long GrnLineId, long? PoLineId, long ItemId, long UomId, long? BinId,
+    decimal Qty, decimal UnitCost, decimal ReceivedValue, HoldStatus HoldStatus, long? BatchId);
+
+public sealed record GrnDto(
+    long GrnId, string DocNo, long? PoId, long VendorId, long WarehouseId, GrnStatus Status,
+    long CreatedBy, DateTime CreatedAt, DateTime? PostedAt, IReadOnlyList<GrnLineDto> Lines);
+
+public sealed record CreatedLayerDto(
+    long LayerId, long ItemId, long WarehouseId, long? BatchId,
+    decimal QtyReceived, decimal QtyRemaining, decimal UnitCost, DateTime ReceiptDate);
+
+public sealed record GrnConfirmResultDto(
+    long GrnId, GrnStatus Status, DateTime PostedAt,
+    IReadOnlyList<CreatedLayerDto> CreatedLayers, IReadOnlyList<long> LedgerRefs, PurchaseOrderStatus? PoStatus);
+
+public sealed record ReleaseLineResultDto(long GrnLineId, HoldStatus HoldStatus);
+
+// Requests ----------------------------------------------------------------------
+
+public sealed class BatchInput
+{
+    [Required, StringLength(50)] public string BatchNo { get; set; } = string.Empty;
+    public DateOnly? ExpiryDate { get; set; }
+}
+
+public sealed class CreateGrnLineInput
+{
+    /// <summary>Set for a PO-based receipt; cost is then derived from the PO line (02-SECURITY C.3).</summary>
+    public long? PoLineId { get; set; }
+    [Required] public long ItemId { get; set; }
+    [Required] public long UomId { get; set; }
+    public long? BinId { get; set; }
+    [Range(0.0001, double.MaxValue)] public decimal Qty { get; set; }
+    /// <summary>Used only for direct (no-PO) receipts; ignored when <see cref="PoLineId"/> is set.</summary>
+    [Range(0, double.MaxValue)] public decimal UnitCost { get; set; }
+    [EnumDataType(typeof(HoldStatus))] public HoldStatus HoldStatus { get; set; } = HoldStatus.Available;
+    public BatchInput? Batch { get; set; }
+}
+
+public sealed class CreateGrnRequest
+{
+    /// <summary>PO to receive against; null for a direct/emergency receipt (FR-GRN-02).</summary>
+    public long? PoId { get; set; }
+    /// <summary>Required for a direct receipt (no PO); ignored otherwise (vendor derives from the PO).</summary>
+    public long? VendorId { get; set; }
+    [Required] public long WarehouseId { get; set; }
+    [Required, MinLength(1)] public List<CreateGrnLineInput> Lines { get; set; } = new();
+}
+
+public sealed class ReleaseLineRequest
+{
+    /// <summary><c>Release</c> makes the stock available; <c>Reject</c> removes it from on-hand.</summary>
+    [Required, RegularExpression("Release|Reject")]
+    public string Action { get; set; } = "Release";
+}

Backend/ERPCore/Dtos/Procurement/PurchaseReturnDtos.cs

@@ -0,0 +1,31 @@
+using System.ComponentModel.DataAnnotations;
+using ERPCore.Domain.Enums;
+
+namespace ERPCore.Dtos.Procurement;
+
+// Responses (docs/11 §3.4) ------------------------------------------------------
+
+public sealed record PurchaseReturnLineDto(long ReturnLineId, long? GrnLineId, long ItemId, decimal Qty);
+
+public sealed record PurchaseReturnDto(
+    long ReturnId, string DocNo, long VendorId, long WarehouseId, long ReasonCodeId, ReturnStatus Status,
+    long CreatedBy, IReadOnlyList<PurchaseReturnLineDto> Lines, IReadOnlyList<long> LedgerRefs);
+
+// Requests ----------------------------------------------------------------------
+
+public sealed class CreatePurchaseReturnLineInput
+{
+    /// <summary>Original GRN line, for traceability against the receipt.</summary>
+    public long? GrnLineId { get; set; }
+    [Required] public long ItemId { get; set; }
+    [Range(0.0001, double.MaxValue)] public decimal Qty { get; set; }
+}
+
+public sealed class CreatePurchaseReturnRequest
+{
+    [Required] public long VendorId { get; set; }
+    [Required] public long WarehouseId { get; set; }
+    /// <summary>Nullable so an omitted value is a distinct <c>REASON_CODE_REQUIRED</c> error.</summary>
+    public long? ReasonCodeId { get; set; }
+    [Required, MinLength(1)] public List<CreatePurchaseReturnLineInput> Lines { get; set; } = new();
+}

Backend/ERPCore/Dtos/Reference/ReasonCodeDtos.cs

@@ -0,0 +1,14 @@
+using System.ComponentModel.DataAnnotations;
+using ERPCore.Domain.Enums;
+
+namespace ERPCore.Dtos.Reference;
+
+/// <summary>Reason code (docs/11 §6).</summary>
+public sealed record ReasonCodeDto(long ReasonCodeId, string Code, string Description, ReasonContext Context);
+
+public sealed class CreateReasonCodeRequest
+{
+    [Required, StringLength(20)] public string Code { get; set; } = string.Empty;
+    [Required, StringLength(200)] public string Description { get; set; } = string.Empty;
+    [Required, EnumDataType(typeof(ReasonContext))] public ReasonContext Context { get; set; }
+}

Backend/ERPCore/Dtos/Stock/AdjustmentDtos.cs

@@ -0,0 +1,31 @@
+using System.ComponentModel.DataAnnotations;
+using ERPCore.Domain.Enums;
+
+namespace ERPCore.Dtos.Stock;
+
+// Responses (docs/11 §5.5) ------------------------------------------------------
+
+public sealed record AdjustmentLineDto(long AdjLineId, long ItemId, long? BinId, long? BatchId, decimal QtyDelta);
+
+public sealed record AdjustmentDto(
+    long AdjustmentId, string DocNo, long WarehouseId, long ReasonCodeId, AdjustmentStatus Status,
+    long CreatedBy, DateTime CreatedAt, IReadOnlyList<AdjustmentLineDto> Lines, IReadOnlyList<long> LedgerRefs);
+
+// Requests ----------------------------------------------------------------------
+
+public sealed class CreateAdjustmentLineInput
+{
+    [Required] public long ItemId { get; set; }
+    public long? BinId { get; set; }
+    public long? BatchId { get; set; }
+    /// <summary>Signed base-UOM delta: negative consumes FIFO layers, positive adds stock.</summary>
+    public decimal QtyDelta { get; set; }
+}
+
+public sealed class CreateAdjustmentRequest
+{
+    [Required] public long WarehouseId { get; set; }
+    /// <summary>Nullable so an omitted value is a distinct <c>REASON_CODE_REQUIRED</c> error, not 0.</summary>
+    public long? ReasonCodeId { get; set; }
+    [Required, MinLength(1)] public List<CreateAdjustmentLineInput> Lines { get; set; } = new();
+}

Backend/ERPCore/Dtos/Stock/CountDtos.cs

@@ -0,0 +1,33 @@
+using System.ComponentModel.DataAnnotations;
+using ERPCore.Domain.Enums;
+
+namespace ERPCore.Dtos.Stock;
+
+// Responses (docs/11 §5.6) ------------------------------------------------------
+
+public sealed record CountLineDto(long CountLineId, long ItemId, long? BinId, decimal SystemQty, decimal? CountedQty, decimal? Variance);
+
+public sealed record CountDto(
+    long CountId, string DocNo, long WarehouseId, CountType CountType, CountStatus Status, IReadOnlyList<CountLineDto> Lines);
+
+public sealed record CountPostResultDto(long CountId, CountStatus Status, long? AdjustmentId, IReadOnlyList<long> LedgerRefs);
+
+// Requests ----------------------------------------------------------------------
+
+public sealed class CreateCountRequest
+{
+    [Required] public long WarehouseId { get; set; }
+    [Required, EnumDataType(typeof(CountType))] public CountType CountType { get; set; }
+    [Required, MinLength(1)] public List<long> ItemIds { get; set; } = new();
+}
+
+public sealed class EnterCountLineInput
+{
+    [Required] public long CountLineId { get; set; }
+    [Range(0, double.MaxValue)] public decimal CountedQty { get; set; }
+}
+
+public sealed class EnterCountsRequest
+{
+    [Required, MinLength(1)] public List<EnterCountLineInput> Lines { get; set; } = new();
+}

Backend/ERPCore/Dtos/Stock/ReorderDtos.cs

@@ -0,0 +1,6 @@
+namespace ERPCore.Dtos.Stock;
+
+/// <summary>An item at/below its reorder point (docs/11 §5.7; FR-STK-10). Computed on read.</summary>
+public sealed record ReorderAlertDto(
+    long ItemId, long WarehouseId, decimal Available,
+    decimal ReorderPoint, decimal ReorderQty, decimal SuggestedRequisitionQty);

Backend/ERPCore/Dtos/Stock/StockDtos.cs

@@ -0,0 +1,22 @@
+using ERPCore.Domain.Enums;
+
+namespace ERPCore.Dtos.Stock;
+
+/// <summary>Stock enquiry (docs/11 §5.1). available = onHand − onHold − reserved − inTransit(out).</summary>
+public sealed record StockOnHandDto(
+    long ItemId, long WarehouseId, decimal OnHand, decimal Available,
+    decimal OnHold, decimal InTransit, decimal Reserved, DateTime AsOf);
+
+/// <summary>A stock-ledger row (docs/11 §5.2).</summary>
+public sealed record StockLedgerRowDto(
+    long LedgerId, long ItemId, long WarehouseId, long? BinId, long? BatchId, long? SerialId,
+    Direction Direction, decimal QtyBase, decimal UnitCost, decimal Value, decimal RunningBalance,
+    string SourceDocType, long SourceDocId, long UserId, DateTime CreatedAt);
+
+/// <summary>An open FIFO layer in a valuation (docs/11 §5.3).</summary>
+public sealed record StockValuationLayerDto(long LayerId, decimal QtyRemaining, decimal UnitCost, decimal Value, DateTime ReceiptDate);
+
+/// <summary>Valuation of on-hand stock from open FIFO layers (docs/11 §5.3).</summary>
+public sealed record StockValuationDto(
+    long ItemId, long WarehouseId, IReadOnlyList<StockValuationLayerDto> Layers,
+    decimal TotalQty, decimal TotalValue, string Currency, string CostingMethod);

Backend/ERPCore/Dtos/Stock/TransferDtos.cs

@@ -0,0 +1,52 @@
+using System.ComponentModel.DataAnnotations;
+using ERPCore.Domain.Enums;
+
+namespace ERPCore.Dtos.Stock;
+
+// Responses (docs/11 §5.4) ------------------------------------------------------
+
+public sealed record TransferLineDto(
+    long TransferLineId, long ItemId, long? SrcBinId, long? DestBinId, long? BatchId, decimal Qty, decimal QtyReceived);
+
+public sealed record TransferDto(
+    long TransferId, string DocNo, long SrcWarehouseId, long DestWarehouseId,
+    TransferStatus Status, IReadOnlyList<TransferLineDto> Lines);
+
+public sealed record ConsumedLayerDto(long LayerId, decimal QtyConsumed, decimal UnitCost);
+
+public sealed record DispatchResultDto(
+    long TransferId, TransferStatus Status, IReadOnlyList<ConsumedLayerDto> ConsumedLayers, IReadOnlyList<long> LedgerRefs);
+
+public sealed record TransferCreatedLayerDto(long LayerId, long WarehouseId, decimal QtyReceived, decimal UnitCost);
+
+public sealed record ReceiveResultDto(
+    long TransferId, TransferStatus Status, IReadOnlyList<TransferCreatedLayerDto> CreatedLayers, IReadOnlyList<long> LedgerRefs);
+
+// Requests ----------------------------------------------------------------------
+
+public sealed class CreateTransferLineInput
+{
+    [Required] public long ItemId { get; set; }
+    public long? SrcBinId { get; set; }
+    public long? DestBinId { get; set; }
+    public long? BatchId { get; set; }
+    [Range(0.0001, double.MaxValue)] public decimal Qty { get; set; }
+}
+
+public sealed class CreateTransferRequest
+{
+    [Required] public long SrcWarehouseId { get; set; }
+    [Required] public long DestWarehouseId { get; set; }
+    [Required, MinLength(1)] public List<CreateTransferLineInput> Lines { get; set; } = new();
+}
+
+public sealed class ReceiveTransferLineInput
+{
+    [Required] public long TransferLineId { get; set; }
+    [Range(0.0001, double.MaxValue)] public decimal Qty { get; set; }
+}
+
+public sealed class ReceiveTransferRequest
+{
+    [Required, MinLength(1)] public List<ReceiveTransferLineInput> Lines { get; set; } = new();
+}

Backend/ERPCore/Infra/Persistence/Auditing/AuditScribe.cs

@@ -0,0 +1,98 @@
+using System.Text.Json;
+using System.Text.Json.Serialization;
+using ERPCore.Domain.Entities;
+using ERPCore.Domain.Enums;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.ChangeTracking;
+
+namespace ERPCore.Infra.Persistence.Auditing;
+
+/// <summary>A mutation captured before save, awaiting its (possibly generated) key.</summary>
+public sealed record PendingAudit(EntityEntry Entry, string EntityType, AuditAction Action, string ChangeSet, long CapturedId, bool IsAdded);
+
+/// <summary>
+/// Builds audit-trail rows from the EF change tracker (FR-X-02). High-volume /
+/// derived / self-referential tables are excluded (the stock ledger is itself the
+/// stock movement audit). Change sets are captured <b>before</b> save so old→new is
+/// accurate; generated keys for inserts are read <b>after</b> save.
+/// </summary>
+public static class AuditScribe
+{
+    private static readonly HashSet<Type> Excluded =
+    [
+        typeof(AuditLog), typeof(JournalEntryStub), typeof(NumberSequence),
+        typeof(StockLedger), typeof(StockLayer),
+    ];
+
+    private static readonly JsonSerializerOptions Json = new()
+    {
+        Converters = { new JsonStringEnumConverter() },
+        DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull,
+    };
+
+    public static List<PendingAudit> Capture(ChangeTracker tracker)
+    {
+        var pending = new List<PendingAudit>();
+        foreach (var entry in tracker.Entries())
+        {
+            if (entry.State is not (EntityState.Added or EntityState.Modified or EntityState.Deleted)) continue;
+            if (Excluded.Contains(entry.Entity.GetType())) continue;
+
+            var action = entry.State switch
+            {
+                EntityState.Added => AuditAction.Create,
+                EntityState.Deleted => AuditAction.Delete,
+                _ => AuditAction.Update,
+            };
+
+            var changeSet = BuildChangeSet(entry, action);
+            if (action == AuditAction.Update && changeSet == "{}") continue; // only concurrency token touched, etc.
+
+            var isAdded = entry.State == EntityState.Added;
+            pending.Add(new PendingAudit(entry, entry.Entity.GetType().Name, action, changeSet, isAdded ? 0 : ReadKey(entry), isAdded));
+        }
+        return pending;
+    }
+
+    public static AuditLog ToLog(PendingAudit p, long userId, DateTime now) => new()
+    {
+        UserId = userId,
+        EntityType = p.EntityType,
+        EntityId = p.IsAdded ? ReadKey(p.Entry) : p.CapturedId,
+        Action = p.Action,
+        ChangeSet = p.ChangeSet,
+        CreatedAt = now,
+    };
+
+    private static long ReadKey(EntityEntry entry)
+    {
+        var pk = entry.Metadata.FindPrimaryKey();
+        if (pk is null || pk.Properties.Count != 1) return 0;
+        var value = entry.Property(pk.Properties[0].Name).CurrentValue;
+        return value is null ? 0 : Convert.ToInt64(value);
+    }
+
+    private static string BuildChangeSet(EntityEntry entry, AuditAction action)
+    {
+        var set = new Dictionary<string, object?>();
+        foreach (var p in entry.Properties)
+        {
+            if (p.Metadata.IsPrimaryKey()) continue;
+            if (p.Metadata.Name == nameof(Item.RowVersion)) continue;
+
+            switch (action)
+            {
+                case AuditAction.Create when p.CurrentValue is not null:
+                    set[p.Metadata.Name] = p.CurrentValue;
+                    break;
+                case AuditAction.Delete:
+                    set[p.Metadata.Name] = p.OriginalValue;
+                    break;
+                case AuditAction.Update when p.IsModified && !Equals(p.OriginalValue, p.CurrentValue):
+                    set[p.Metadata.Name] = new Dictionary<string, object?> { ["old"] = p.OriginalValue, ["new"] = p.CurrentValue };
+                    break;
+            }
+        }
+        return JsonSerializer.Serialize(set, Json);
+    }
+}

Backend/ERPCore/Infra/Persistence/Configurations/AuditConfiguration.cs

@@ -0,0 +1,41 @@
+using ERPCore.Domain.Entities;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Metadata.Builders;
+
+namespace ERPCore.Infra.Persistence.Configurations;
+
+public sealed class AuditLogConfiguration : IEntityTypeConfiguration<AuditLog>
+{
+    public void Configure(EntityTypeBuilder<AuditLog> builder)
+    {
+        builder.ToTable("audit_logs");
+        builder.HasKey(a => a.AuditId);
+
+        builder.Property(a => a.EntityType).IsRequired().HasMaxLength(80);
+        builder.Property(a => a.Action).HasConversion<string>().HasMaxLength(10).IsRequired();
+        builder.Property(a => a.ChangeSet).IsRequired().HasColumnType("jsonb");
+        builder.Property(a => a.CreatedAt).IsRequired();
+
+        builder.HasOne<User>().WithMany().HasForeignKey(a => a.UserId).OnDelete(DeleteBehavior.Restrict);
+
+        builder.HasIndex(a => new { a.EntityType, a.EntityId });
+        builder.HasIndex(a => a.CreatedAt);
+        builder.HasIndex(a => a.UserId);
+    }
+}
+
+public sealed class JournalEntryStubConfiguration : IEntityTypeConfiguration<JournalEntryStub>
+{
+    public void Configure(EntityTypeBuilder<JournalEntryStub> builder)
+    {
+        builder.ToTable("journal_entry_stubs");
+        builder.HasKey(j => j.JournalId);
+
+        builder.Property(j => j.SourceDocType).IsRequired().HasMaxLength(10);
+        builder.Property(j => j.DebitAccount).IsRequired().HasMaxLength(20);
+        builder.Property(j => j.CreditAccount).IsRequired().HasMaxLength(20);
+        builder.Property(j => j.Amount).HasPrecision(18, 4);
+
+        builder.HasIndex(j => new { j.SourceDocType, j.SourceDocId });
+    }
+}

Backend/ERPCore/Infra/Persistence/Configurations/BatchSerialConfiguration.cs

@@ -0,0 +1,43 @@
+using ERPCore.Domain.Entities;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Metadata.Builders;
+
+namespace ERPCore.Infra.Persistence.Configurations;
+
+public sealed class BatchConfiguration : IEntityTypeConfiguration<Batch>
+{
+    public void Configure(EntityTypeBuilder<Batch> builder)
+    {
+        builder.ToTable("batches");
+        builder.HasKey(b => b.BatchId);
+
+        builder.Property(b => b.BatchNo).IsRequired().HasMaxLength(50);
+
+        builder.HasOne(b => b.Item)
+            .WithMany()
+            .HasForeignKey(b => b.ItemId)
+            .OnDelete(DeleteBehavior.Restrict);
+
+        // Batch number unique within an item.
+        builder.HasIndex(b => new { b.ItemId, b.BatchNo }).IsUnique();
+    }
+}
+
+public sealed class SerialConfiguration : IEntityTypeConfiguration<Serial>
+{
+    public void Configure(EntityTypeBuilder<Serial> builder)
+    {
+        builder.ToTable("serials");
+        builder.HasKey(s => s.SerialId);
+
+        builder.Property(s => s.SerialNo).IsRequired().HasMaxLength(100);
+        builder.Property(s => s.Status).IsRequired().HasMaxLength(20);
+
+        builder.HasOne(s => s.Item)
+            .WithMany()
+            .HasForeignKey(s => s.ItemId)
+            .OnDelete(DeleteBehavior.Restrict);
+
+        builder.HasIndex(s => new { s.ItemId, s.SerialNo }).IsUnique();
+    }
+}

Backend/ERPCore/Infra/Persistence/Configurations/GrnConfiguration.cs

@@ -0,0 +1,50 @@
+using ERPCore.Domain.Entities;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Metadata.Builders;
+
+namespace ERPCore.Infra.Persistence.Configurations;
+
+public sealed class GrnConfiguration : IEntityTypeConfiguration<Grn>
+{
+    public void Configure(EntityTypeBuilder<Grn> builder)
+    {
+        builder.ToTable("grns");
+        builder.HasKey(g => g.GrnId);
+
+        builder.Property(g => g.DocNo).IsRequired().HasMaxLength(30);
+        builder.HasIndex(g => g.DocNo).IsUnique();
+
+        builder.Property(g => g.Status).HasConversion<string>().HasMaxLength(20).IsRequired();
+        builder.Property(g => g.CreatedAt).IsRequired();
+        builder.Property(g => g.RowVersion).IsRowVersion();
+
+        builder.HasOne(g => g.PurchaseOrder).WithMany().HasForeignKey(g => g.PoId).OnDelete(DeleteBehavior.Restrict);
+        builder.HasOne(g => g.Vendor).WithMany().HasForeignKey(g => g.VendorId).OnDelete(DeleteBehavior.Restrict);
+        builder.HasOne(g => g.Warehouse).WithMany().HasForeignKey(g => g.WarehouseId).OnDelete(DeleteBehavior.Restrict);
+        builder.HasOne(g => g.Creator).WithMany().HasForeignKey(g => g.CreatedBy).OnDelete(DeleteBehavior.Restrict);
+
+        builder.HasIndex(g => g.Status);
+        builder.HasIndex(g => g.PoId);
+    }
+}
+
+public sealed class GrnLineConfiguration : IEntityTypeConfiguration<GrnLine>
+{
+    public void Configure(EntityTypeBuilder<GrnLine> builder)
+    {
+        builder.ToTable("grn_lines");
+        builder.HasKey(l => l.GrnLineId);
+
+        builder.Property(l => l.Qty).HasPrecision(18, 4);
+        builder.Property(l => l.UnitCost).HasPrecision(18, 6);
+        builder.Property(l => l.ReceivedValue).HasPrecision(18, 4);
+        builder.Property(l => l.HoldStatus).HasConversion<string>().HasMaxLength(20).IsRequired();
+
+        builder.HasOne(l => l.Grn).WithMany(g => g.Lines).HasForeignKey(l => l.GrnId).OnDelete(DeleteBehavior.Cascade);
+        builder.HasOne(l => l.PoLine).WithMany().HasForeignKey(l => l.PoLineId).OnDelete(DeleteBehavior.Restrict);
+        builder.HasOne(l => l.Item).WithMany().HasForeignKey(l => l.ItemId).OnDelete(DeleteBehavior.Restrict);
+        builder.HasOne(l => l.Uom).WithMany().HasForeignKey(l => l.UomId).OnDelete(DeleteBehavior.Restrict);
+        builder.HasOne(l => l.Bin).WithMany().HasForeignKey(l => l.BinId).OnDelete(DeleteBehavior.Restrict);
+        builder.HasOne(l => l.Batch).WithMany().HasForeignKey(l => l.BatchId).OnDelete(DeleteBehavior.Restrict);
+    }
+}

Backend/ERPCore/Infra/Persistence/Configurations/PurchaseReturnConfiguration.cs

@@ -0,0 +1,40 @@
+using ERPCore.Domain.Entities;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Metadata.Builders;
+
+namespace ERPCore.Infra.Persistence.Configurations;
+
+public sealed class PurchaseReturnConfiguration : IEntityTypeConfiguration<PurchaseReturn>
+{
+    public void Configure(EntityTypeBuilder<PurchaseReturn> builder)
+    {
+        builder.ToTable("purchase_returns");
+        builder.HasKey(r => r.ReturnId);
+
+        builder.Property(r => r.DocNo).IsRequired().HasMaxLength(30);
+        builder.HasIndex(r => r.DocNo).IsUnique();
+
+        builder.Property(r => r.Status).HasConversion<string>().HasMaxLength(20).IsRequired();
+        builder.Property(r => r.CreatedAt).IsRequired();
+
+        builder.HasOne(r => r.Vendor).WithMany().HasForeignKey(r => r.VendorId).OnDelete(DeleteBehavior.Restrict);
+        builder.HasOne(r => r.Warehouse).WithMany().HasForeignKey(r => r.WarehouseId).OnDelete(DeleteBehavior.Restrict);
+        builder.HasOne(r => r.ReasonCode).WithMany().HasForeignKey(r => r.ReasonCodeId).OnDelete(DeleteBehavior.Restrict);
+        builder.HasOne(r => r.Creator).WithMany().HasForeignKey(r => r.CreatedBy).OnDelete(DeleteBehavior.Restrict);
+    }
+}
+
+public sealed class PurchaseReturnLineConfiguration : IEntityTypeConfiguration<PurchaseReturnLine>
+{
+    public void Configure(EntityTypeBuilder<PurchaseReturnLine> builder)
+    {
+        builder.ToTable("purchase_return_lines");
+        builder.HasKey(l => l.ReturnLineId);
+
+        builder.Property(l => l.Qty).HasPrecision(18, 4);
+
+        builder.HasOne(l => l.Return).WithMany(r => r.Lines).HasForeignKey(l => l.ReturnId).OnDelete(DeleteBehavior.Cascade);
+        builder.HasOne(l => l.GrnLine).WithMany().HasForeignKey(l => l.GrnLineId).OnDelete(DeleteBehavior.Restrict);
+        builder.HasOne(l => l.Item).WithMany().HasForeignKey(l => l.ItemId).OnDelete(DeleteBehavior.Restrict);
+    }
+}

Backend/ERPCore/Infra/Persistence/Configurations/ReasonCodeConfiguration.cs

@@ -0,0 +1,20 @@
+using ERPCore.Domain.Entities;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Metadata.Builders;
+
+namespace ERPCore.Infra.Persistence.Configurations;
+
+public sealed class ReasonCodeConfiguration : IEntityTypeConfiguration<ReasonCode>
+{
+    public void Configure(EntityTypeBuilder<ReasonCode> builder)
+    {
+        builder.ToTable("reason_codes");
+        builder.HasKey(r => r.ReasonCodeId);
+
+        builder.Property(r => r.Code).IsRequired().HasMaxLength(20);
+        builder.Property(r => r.Description).IsRequired().HasMaxLength(200);
+        builder.Property(r => r.Context).HasConversion<string>().HasMaxLength(20).IsRequired();
+
+        builder.HasIndex(r => new { r.Context, r.Code }).IsUnique();
+    }
+}

Backend/ERPCore/Infra/Persistence/Configurations/StockAdjustmentConfiguration.cs

@@ -0,0 +1,42 @@
+using ERPCore.Domain.Entities;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Metadata.Builders;
+
+namespace ERPCore.Infra.Persistence.Configurations;
+
+public sealed class StockAdjustmentConfiguration : IEntityTypeConfiguration<StockAdjustment>
+{
+    public void Configure(EntityTypeBuilder<StockAdjustment> builder)
+    {
+        builder.ToTable("stock_adjustments");
+        builder.HasKey(a => a.AdjustmentId);
+
+        builder.Property(a => a.DocNo).IsRequired().HasMaxLength(30);
+        builder.HasIndex(a => a.DocNo).IsUnique();
+
+        builder.Property(a => a.Status).HasConversion<string>().HasMaxLength(20).IsRequired();
+        builder.Property(a => a.CreatedAt).IsRequired();
+        builder.Property(a => a.RowVersion).IsRowVersion();
+
+        builder.HasOne(a => a.Warehouse).WithMany().HasForeignKey(a => a.WarehouseId).OnDelete(DeleteBehavior.Restrict);
+        builder.HasOne(a => a.ReasonCode).WithMany().HasForeignKey(a => a.ReasonCodeId).OnDelete(DeleteBehavior.Restrict);
+        builder.HasOne(a => a.Creator).WithMany().HasForeignKey(a => a.CreatedBy).OnDelete(DeleteBehavior.Restrict);
+    }
+}
+
+public sealed class StockAdjustmentLineConfiguration : IEntityTypeConfiguration<StockAdjustmentLine>
+{
+    public void Configure(EntityTypeBuilder<StockAdjustmentLine> builder)
+    {
+        builder.ToTable("stock_adjustment_lines");
+        builder.HasKey(l => l.AdjLineId);
+
+        builder.Property(l => l.QtyDelta).HasPrecision(18, 4);
+
+        builder.HasOne(l => l.Adjustment).WithMany(a => a.Lines).HasForeignKey(l => l.AdjustmentId).OnDelete(DeleteBehavior.Cascade);
+        builder.HasOne(l => l.Item).WithMany().HasForeignKey(l => l.ItemId).OnDelete(DeleteBehavior.Restrict);
+        builder.HasOne<Bin>().WithMany().HasForeignKey(l => l.BinId).OnDelete(DeleteBehavior.Restrict);
+        builder.HasOne<Batch>().WithMany().HasForeignKey(l => l.BatchId).OnDelete(DeleteBehavior.Restrict);
+        builder.HasOne<Serial>().WithMany().HasForeignKey(l => l.SerialId).OnDelete(DeleteBehavior.Restrict);
+    }
+}

Backend/ERPCore/Infra/Persistence/Configurations/StockConfiguration.cs

@@ -0,0 +1,60 @@
+using ERPCore.Domain.Entities;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Metadata.Builders;
+
+namespace ERPCore.Infra.Persistence.Configurations;
+
+public sealed class StockLayerConfiguration : IEntityTypeConfiguration<StockLayer>
+{
+    public void Configure(EntityTypeBuilder<StockLayer> builder)
+    {
+        builder.ToTable("stock_layers");
+        builder.HasKey(l => l.LayerId);
+
+        builder.Property(l => l.QtyReceived).HasPrecision(18, 4);
+        builder.Property(l => l.QtyRemaining).HasPrecision(18, 4);
+        builder.Property(l => l.UnitCost).HasPrecision(18, 6);
+        builder.Property(l => l.ReceiptDate).IsRequired();
+
+        builder.HasOne(l => l.Item).WithMany().HasForeignKey(l => l.ItemId).OnDelete(DeleteBehavior.Restrict);
+        builder.HasOne(l => l.Warehouse).WithMany().HasForeignKey(l => l.WarehouseId).OnDelete(DeleteBehavior.Restrict);
+        builder.HasOne(l => l.Batch).WithMany().HasForeignKey(l => l.BatchId).OnDelete(DeleteBehavior.Restrict);
+        builder.HasOne(l => l.Serial).WithMany().HasForeignKey(l => l.SerialId).OnDelete(DeleteBehavior.Restrict);
+        builder.HasOne(l => l.GrnLine).WithMany().HasForeignKey(l => l.GrnLineId).OnDelete(DeleteBehavior.Restrict);
+
+        // FIFO consumption orders by receipt date then layer id, scoped per item+warehouse.
+        builder.HasIndex(l => new { l.ItemId, l.WarehouseId, l.ReceiptDate, l.LayerId });
+        builder.HasIndex(l => l.GrnLineId);
+    }
+}
+
+public sealed class StockLedgerConfiguration : IEntityTypeConfiguration<StockLedger>
+{
+    public void Configure(EntityTypeBuilder<StockLedger> builder)
+    {
+        // Append-only (FR-STK-01/FR-X-05): the app never updates/deletes ledger rows.
+        // DB-level revocation of UPDATE/DELETE is a deferred hardening step (02-SECURITY B.3).
+        builder.ToTable("stock_ledger");
+        builder.HasKey(l => l.LedgerId);
+
+        builder.Property(l => l.Direction).HasConversion<string>().HasMaxLength(5).IsRequired();
+        builder.Property(l => l.QtyBase).HasPrecision(18, 4);
+        builder.Property(l => l.UnitCost).HasPrecision(18, 6);
+        builder.Property(l => l.Value).HasPrecision(18, 4);
+        builder.Property(l => l.RunningBalance).HasPrecision(18, 4);
+        builder.Property(l => l.SourceDocType).IsRequired().HasMaxLength(10);
+        builder.Property(l => l.CreatedAt).IsRequired();
+
+        builder.HasOne<Item>().WithMany().HasForeignKey(l => l.ItemId).OnDelete(DeleteBehavior.Restrict);
+        builder.HasOne<Warehouse>().WithMany().HasForeignKey(l => l.WarehouseId).OnDelete(DeleteBehavior.Restrict);
+        builder.HasOne<User>().WithMany().HasForeignKey(l => l.UserId).OnDelete(DeleteBehavior.Restrict);
+        builder.HasOne<Bin>().WithMany().HasForeignKey(l => l.BinId).OnDelete(DeleteBehavior.Restrict);
+        builder.HasOne<Batch>().WithMany().HasForeignKey(l => l.BatchId).OnDelete(DeleteBehavior.Restrict);
+        builder.HasOne<Serial>().WithMany().HasForeignKey(l => l.SerialId).OnDelete(DeleteBehavior.Restrict);
+
+        // Time-series query paths (NFR-06) and polymorphic source tracing.
+        builder.HasIndex(l => new { l.ItemId, l.WarehouseId, l.LedgerId });
+        builder.HasIndex(l => new { l.ItemId, l.WarehouseId, l.CreatedAt });
+        builder.HasIndex(l => new { l.SourceDocType, l.SourceDocId });
+    }
+}

Backend/ERPCore/Infra/Persistence/Configurations/StockCountConfiguration.cs

@@ -0,0 +1,44 @@
+using ERPCore.Domain.Entities;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Metadata.Builders;
+
+namespace ERPCore.Infra.Persistence.Configurations;
+
+public sealed class StockCountConfiguration : IEntityTypeConfiguration<StockCount>
+{
+    public void Configure(EntityTypeBuilder<StockCount> builder)
+    {
+        builder.ToTable("stock_counts");
+        builder.HasKey(c => c.CountId);
+
+        builder.Property(c => c.DocNo).IsRequired().HasMaxLength(30);
+        builder.HasIndex(c => c.DocNo).IsUnique();
+
+        builder.Property(c => c.CountType).HasConversion<string>().HasMaxLength(20).IsRequired();
+        builder.Property(c => c.Status).HasConversion<string>().HasMaxLength(20).IsRequired();
+        builder.Property(c => c.CreatedAt).IsRequired();
+        builder.Property(c => c.RowVersion).IsRowVersion();
+
+        builder.HasOne(c => c.Warehouse).WithMany().HasForeignKey(c => c.WarehouseId).OnDelete(DeleteBehavior.Restrict);
+        builder.HasOne(c => c.Creator).WithMany().HasForeignKey(c => c.CreatedBy).OnDelete(DeleteBehavior.Restrict);
+
+        builder.HasIndex(c => c.Status);
+    }
+}
+
+public sealed class StockCountLineConfiguration : IEntityTypeConfiguration<StockCountLine>
+{
+    public void Configure(EntityTypeBuilder<StockCountLine> builder)
+    {
+        builder.ToTable("stock_count_lines");
+        builder.HasKey(l => l.CountLineId);
+
+        builder.Property(l => l.SystemQty).HasPrecision(18, 4);
+        builder.Property(l => l.CountedQty).HasPrecision(18, 4);
+        builder.Property(l => l.Variance).HasPrecision(18, 4);
+
+        builder.HasOne(l => l.Count).WithMany(c => c.Lines).HasForeignKey(l => l.CountId).OnDelete(DeleteBehavior.Cascade);
+        builder.HasOne(l => l.Item).WithMany().HasForeignKey(l => l.ItemId).OnDelete(DeleteBehavior.Restrict);
+        builder.HasOne<Bin>().WithMany().HasForeignKey(l => l.BinId).OnDelete(DeleteBehavior.Restrict);
+    }
+}

Backend/ERPCore/Infra/Persistence/Configurations/StockTransferConfiguration.cs

@@ -0,0 +1,47 @@
+using ERPCore.Domain.Entities;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Metadata.Builders;
+
+namespace ERPCore.Infra.Persistence.Configurations;
+
+public sealed class StockTransferConfiguration : IEntityTypeConfiguration<StockTransfer>
+{
+    public void Configure(EntityTypeBuilder<StockTransfer> builder)
+    {
+        builder.ToTable("stock_transfers");
+        builder.HasKey(t => t.TransferId);
+
+        builder.Property(t => t.DocNo).IsRequired().HasMaxLength(30);
+        builder.HasIndex(t => t.DocNo).IsUnique();
+
+        builder.Property(t => t.Status).HasConversion<string>().HasMaxLength(20).IsRequired();
+        builder.Property(t => t.CreatedAt).IsRequired();
+        builder.Property(t => t.RowVersion).IsRowVersion();
+
+        builder.HasOne(t => t.SrcWarehouse).WithMany().HasForeignKey(t => t.SrcWarehouseId).OnDelete(DeleteBehavior.Restrict);
+        builder.HasOne(t => t.DestWarehouse).WithMany().HasForeignKey(t => t.DestWarehouseId).OnDelete(DeleteBehavior.Restrict);
+        builder.HasOne(t => t.Creator).WithMany().HasForeignKey(t => t.CreatedBy).OnDelete(DeleteBehavior.Restrict);
+
+        builder.HasIndex(t => t.Status);
+    }
+}
+
+public sealed class StockTransferLineConfiguration : IEntityTypeConfiguration<StockTransferLine>
+{
+    public void Configure(EntityTypeBuilder<StockTransferLine> builder)
+    {
+        builder.ToTable("stock_transfer_lines");
+        builder.HasKey(l => l.TransferLineId);
+
+        builder.Property(l => l.Qty).HasPrecision(18, 4);
+        builder.Property(l => l.UnitCost).HasPrecision(18, 6);
+        builder.Property(l => l.QtyReceived).HasPrecision(18, 4);
+
+        builder.HasOne(l => l.Transfer).WithMany(t => t.Lines).HasForeignKey(l => l.TransferId).OnDelete(DeleteBehavior.Cascade);
+        builder.HasOne(l => l.Item).WithMany().HasForeignKey(l => l.ItemId).OnDelete(DeleteBehavior.Restrict);
+        builder.HasOne<Bin>().WithMany().HasForeignKey(l => l.SrcBinId).OnDelete(DeleteBehavior.Restrict);
+        builder.HasOne<Bin>().WithMany().HasForeignKey(l => l.DestBinId).OnDelete(DeleteBehavior.Restrict);
+        builder.HasOne<Batch>().WithMany().HasForeignKey(l => l.BatchId).OnDelete(DeleteBehavior.Restrict);
+        builder.HasOne<Serial>().WithMany().HasForeignKey(l => l.SerialId).OnDelete(DeleteBehavior.Restrict);
+    }
+}

Backend/ERPCore/Infra/Persistence/DataSeeder.cs

@@ -0,0 +1,45 @@
+using ERPCore.Domain.Entities;
+using ERPCore.Domain.Enums;
+using Microsoft.EntityFrameworkCore;
+
+namespace ERPCore.Infra.Persistence;
+
+/// <summary>
+/// Idempotent startup seeding of configurable reference data (docs/10 §B.8.3).
+/// Reason codes are seeded at runtime (not via <c>HasData</c>) so the identity
+/// sequence advances normally and later admin <c>POST /reason-codes</c> calls
+/// cannot collide with seeded ids.
+/// </summary>
+public static class DataSeeder
+{
+    private static readonly (string Code, string Description, ReasonContext Context)[] StandardReasonCodes =
+    [
+        ("DMG", "Damage", ReasonContext.Adjustment),
+        ("THEFT", "Theft/Loss", ReasonContext.Adjustment),
+        ("VAR", "Count Variance", ReasonContext.Adjustment),
+        ("EXP", "Expiry Write-off", ReasonContext.Adjustment),
+        ("SYS", "System Correction", ReasonContext.Adjustment),
+        ("DEF", "Defective", ReasonContext.Return),
+        ("WRONG", "Wrong Item", ReasonContext.Return),
+        ("OVER", "Over-supply", ReasonContext.Return),
+        ("QREJ", "Quality Reject", ReasonContext.Return),
+    ];
+
+    public static async Task SeedAsync(ErpDbContext db, CancellationToken ct = default)
+    {
+        var existing = await db.ReasonCodes
+            .Select(r => new { r.Context, r.Code })
+            .ToListAsync(ct);
+        var have = existing.Select(x => (x.Context, x.Code)).ToHashSet();
+
+        var toAdd = StandardReasonCodes
+            .Where(r => !have.Contains((r.Context, r.Code)))
+            .Select(r => new ReasonCode { Code = r.Code, Description = r.Description, Context = r.Context })
+            .ToList();
+
+        if (toAdd.Count == 0) return;
+
+        db.ReasonCodes.AddRange(toAdd);
+        await db.SaveChangesAsync(ct);
+    }
+}

Backend/ERPCore/Infra/Persistence/ErpDbContext.cs

@@ -1,4 +1,6 @@
 using ERPCore.Domain.Entities;
+using ERPCore.Infra.Auth;
+using ERPCore.Infra.Persistence.Auditing;
 using Microsoft.EntityFrameworkCore;
 
 namespace ERPCore.Infra.Persistence;
@@ -8,11 +10,15 @@ namespace ERPCore.Infra.Persistence;
 /// <see cref="IEntityTypeConfiguration{TEntity}"/> configurations are added under
 /// Domain/Entities and Infra/Persistence/Configurations as they are implemented.
 /// The authoritative schema lives in docs/10-BACKEND-PHASE1.md — do not invent it here.
+/// Every save writes an immutable audit trail (FR-X-02) via <see cref="AuditScribe"/>.
 /// </summary>
 public class ErpDbContext : DbContext
 {
-    public ErpDbContext(DbContextOptions<ErpDbContext> options) : base(options)
+    private readonly ICurrentUser _currentUser;
+
+    public ErpDbContext(DbContextOptions<ErpDbContext> options, ICurrentUser currentUser) : base(options)
     {
+        _currentUser = currentUser;
     }
 
     // --- Master Data (docs/10 Part C.1) ---
@@ -39,6 +45,37 @@ public class ErpDbContext : DbContext
     public DbSet<PurchaseOrder> PurchaseOrders => Set<PurchaseOrder>();
     public DbSet<PoLine> PoLines => Set<PoLine>();
 
+    // --- Goods Receipt (docs/10 Part C.3) ---
+    public DbSet<Grn> Grns => Set<Grn>();
+    public DbSet<GrnLine> GrnLines => Set<GrnLine>();
+
+    // --- Batch / Serial (docs/10 Part C.4) ---
+    public DbSet<Batch> Batches => Set<Batch>();
+    public DbSet<Serial> Serials => Set<Serial>();
+
+    // --- Stock core: FIFO layers + immutable ledger (docs/10 Part C.5) ---
+    public DbSet<StockLayer> StockLayers => Set<StockLayer>();
+    public DbSet<StockLedger> StockLedger => Set<StockLedger>();
+
+    // --- Stock transactions (docs/10 Part C.6) ---
+    public DbSet<StockTransfer> StockTransfers => Set<StockTransfer>();
+    public DbSet<StockTransferLine> StockTransferLines => Set<StockTransferLine>();
+    public DbSet<StockAdjustment> StockAdjustments => Set<StockAdjustment>();
+    public DbSet<StockAdjustmentLine> StockAdjustmentLines => Set<StockAdjustmentLine>();
+    public DbSet<StockCount> StockCounts => Set<StockCount>();
+    public DbSet<StockCountLine> StockCountLines => Set<StockCountLine>();
+
+    // --- Purchase returns (docs/10 Part C.2) ---
+    public DbSet<PurchaseReturn> PurchaseReturns => Set<PurchaseReturn>();
+    public DbSet<PurchaseReturnLine> PurchaseReturnLines => Set<PurchaseReturnLine>();
+
+    // --- Reference data (docs/10 Part C.7) ---
+    public DbSet<ReasonCode> ReasonCodes => Set<ReasonCode>();
+
+    // --- Cross-cutting: audit trail + GL-ready journal (docs/10 Part C.7) ---
+    public DbSet<AuditLog> AuditLogs => Set<AuditLog>();
+    public DbSet<JournalEntryStub> JournalEntryStubs => Set<JournalEntryStub>();
+
     protected override void OnModelCreating(ModelBuilder modelBuilder)
     {
         base.OnModelCreating(modelBuilder);
@@ -47,4 +84,39 @@ public class ErpDbContext : DbContext
         // (Infra/Persistence/Configurations/*).
         modelBuilder.ApplyConfigurationsFromAssembly(typeof(ErpDbContext).Assembly);
     }
+
+    // Audit trail (FR-X-02): capture mutations before save (accurate old→new), then
+    // write the log rows once inserts have their generated keys. A second base save
+    // persists the logs without re-auditing them.
+    public override async Task<int> SaveChangesAsync(bool acceptAllChangesOnSuccess, CancellationToken ct = default)
+    {
+        var pending = AuditScribe.Capture(ChangeTracker);
+        var result = await base.SaveChangesAsync(acceptAllChangesOnSuccess, ct);
+        if (pending.Count > 0)
+        {
+            WriteAuditLogs(pending);
+            await base.SaveChangesAsync(acceptAllChangesOnSuccess, ct);
+        }
+        return result;
+    }
+
+    public override int SaveChanges(bool acceptAllChangesOnSuccess)
+    {
+        var pending = AuditScribe.Capture(ChangeTracker);
+        var result = base.SaveChanges(acceptAllChangesOnSuccess);
+        if (pending.Count > 0)
+        {
+            WriteAuditLogs(pending);
+            base.SaveChanges(acceptAllChangesOnSuccess);
+        }
+        return result;
+    }
+
+    private void WriteAuditLogs(IReadOnlyList<PendingAudit> pending)
+    {
+        var now = DateTime.UtcNow;
+        var userId = _currentUser.AuditUserId;
+        foreach (var p in pending)
+            AuditLogs.Add(AuditScribe.ToLog(p, userId, now));
+    }
 }

Backend/ERPCore/Infra/Persistence/Migrations/20260713054124_AddStockAndGrn.cs

@@ -0,0 +1,434 @@
+using System;
+using Microsoft.EntityFrameworkCore.Migrations;
+using Npgsql.EntityFrameworkCore.PostgreSQL.Metadata;
+
+#nullable disable
+
+namespace ERPCore.Infra.Persistence.Migrations
+{
+    /// <inheritdoc />
+    public partial class AddStockAndGrn : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.CreateTable(
+                name: "batches",
+                columns: table => new
+                {
+                    BatchId = table.Column<long>(type: "bigint", nullable: false)
+                        .Annotation("Npgsql:ValueGenerationStrategy", NpgsqlValueGenerationStrategy.IdentityByDefaultColumn),
+                    ItemId = table.Column<long>(type: "bigint", nullable: false),
+                    BatchNo = table.Column<string>(type: "character varying(50)", maxLength: 50, nullable: false),
+                    ExpiryDate = table.Column<DateOnly>(type: "date", nullable: true)
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("PK_batches", x => x.BatchId);
+                    table.ForeignKey(
+                        name: "FK_batches_items_ItemId",
+                        column: x => x.ItemId,
+                        principalTable: "items",
+                        principalColumn: "ItemId",
+                        onDelete: ReferentialAction.Restrict);
+                });
+
+            migrationBuilder.CreateTable(
+                name: "grns",
+                columns: table => new
+                {
+                    GrnId = table.Column<long>(type: "bigint", nullable: false)
+                        .Annotation("Npgsql:ValueGenerationStrategy", NpgsqlValueGenerationStrategy.IdentityByDefaultColumn),
+                    DocNo = table.Column<string>(type: "character varying(30)", maxLength: 30, nullable: false),
+                    PoId = table.Column<long>(type: "bigint", nullable: true),
+                    VendorId = table.Column<long>(type: "bigint", nullable: false),
+                    WarehouseId = table.Column<long>(type: "bigint", nullable: false),
+                    Status = table.Column<string>(type: "character varying(20)", maxLength: 20, nullable: false),
+                    CreatedBy = table.Column<long>(type: "bigint", nullable: false),
+                    CreatedAt = table.Column<DateTime>(type: "timestamp with time zone", nullable: false),
+                    PostedAt = table.Column<DateTime>(type: "timestamp with time zone", nullable: true),
+                    xmin = table.Column<uint>(type: "xid", rowVersion: true, nullable: false)
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("PK_grns", x => x.GrnId);
+                    table.ForeignKey(
+                        name: "FK_grns_purchase_orders_PoId",
+                        column: x => x.PoId,
+                        principalTable: "purchase_orders",
+                        principalColumn: "PoId",
+                        onDelete: ReferentialAction.Restrict);
+                    table.ForeignKey(
+                        name: "FK_grns_users_CreatedBy",
+                        column: x => x.CreatedBy,
+                        principalTable: "users",
+                        principalColumn: "UserId",
+                        onDelete: ReferentialAction.Restrict);
+                    table.ForeignKey(
+                        name: "FK_grns_vendors_VendorId",
+                        column: x => x.VendorId,
+                        principalTable: "vendors",
+                        principalColumn: "VendorId",
+                        onDelete: ReferentialAction.Restrict);
+                    table.ForeignKey(
+                        name: "FK_grns_warehouses_WarehouseId",
+                        column: x => x.WarehouseId,
+                        principalTable: "warehouses",
+                        principalColumn: "WarehouseId",
+                        onDelete: ReferentialAction.Restrict);
+                });
+
+            migrationBuilder.CreateTable(
+                name: "serials",
+                columns: table => new
+                {
+                    SerialId = table.Column<long>(type: "bigint", nullable: false)
+                        .Annotation("Npgsql:ValueGenerationStrategy", NpgsqlValueGenerationStrategy.IdentityByDefaultColumn),
+                    ItemId = table.Column<long>(type: "bigint", nullable: false),
+                    SerialNo = table.Column<string>(type: "character varying(100)", maxLength: 100, nullable: false),
+                    Status = table.Column<string>(type: "character varying(20)", maxLength: 20, nullable: false)
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("PK_serials", x => x.SerialId);
+                    table.ForeignKey(
+                        name: "FK_serials_items_ItemId",
+                        column: x => x.ItemId,
+                        principalTable: "items",
+                        principalColumn: "ItemId",
+                        onDelete: ReferentialAction.Restrict);
+                });
+
+            migrationBuilder.CreateTable(
+                name: "grn_lines",
+                columns: table => new
+                {
+                    GrnLineId = table.Column<long>(type: "bigint", nullable: false)
+                        .Annotation("Npgsql:ValueGenerationStrategy", NpgsqlValueGenerationStrategy.IdentityByDefaultColumn),
+                    GrnId = table.Column<long>(type: "bigint", nullable: false),
+                    PoLineId = table.Column<long>(type: "bigint", nullable: true),
+                    ItemId = table.Column<long>(type: "bigint", nullable: false),
+                    UomId = table.Column<long>(type: "bigint", nullable: false),
+                    BinId = table.Column<long>(type: "bigint", nullable: true),
+                    BatchId = table.Column<long>(type: "bigint", nullable: true),
+                    Qty = table.Column<decimal>(type: "numeric(18,4)", precision: 18, scale: 4, nullable: false),
+                    UnitCost = table.Column<decimal>(type: "numeric(18,6)", precision: 18, scale: 6, nullable: false),
+                    ReceivedValue = table.Column<decimal>(type: "numeric(18,4)", precision: 18, scale: 4, nullable: false),
+                    HoldStatus = table.Column<string>(type: "character varying(20)", maxLength: 20, nullable: false)
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("PK_grn_lines", x => x.GrnLineId);
+                    table.ForeignKey(
+                        name: "FK_grn_lines_batches_BatchId",
+                        column: x => x.BatchId,
+                        principalTable: "batches",
+                        principalColumn: "BatchId",
+                        onDelete: ReferentialAction.Restrict);
+                    table.ForeignKey(
+                        name: "FK_grn_lines_bins_BinId",
+                        column: x => x.BinId,
+                        principalTable: "bins",
+                        principalColumn: "BinId",
+                        onDelete: ReferentialAction.Restrict);
+                    table.ForeignKey(
+                        name: "FK_grn_lines_grns_GrnId",
+                        column: x => x.GrnId,
+                        principalTable: "grns",
+                        principalColumn: "GrnId",
+                        onDelete: ReferentialAction.Cascade);
+                    table.ForeignKey(
+                        name: "FK_grn_lines_items_ItemId",
+                        column: x => x.ItemId,
+                        principalTable: "items",
+                        principalColumn: "ItemId",
+                        onDelete: ReferentialAction.Restrict);
+                    table.ForeignKey(
+                        name: "FK_grn_lines_po_lines_PoLineId",
+                        column: x => x.PoLineId,
+                        principalTable: "po_lines",
+                        principalColumn: "PoLineId",
+                        onDelete: ReferentialAction.Restrict);
+                    table.ForeignKey(
+                        name: "FK_grn_lines_uoms_UomId",
+                        column: x => x.UomId,
+                        principalTable: "uoms",
+                        principalColumn: "UomId",
+                        onDelete: ReferentialAction.Restrict);
+                });
+
+            migrationBuilder.CreateTable(
+                name: "stock_ledger",
+                columns: table => new
+                {
+                    LedgerId = table.Column<long>(type: "bigint", nullable: false)
+                        .Annotation("Npgsql:ValueGenerationStrategy", NpgsqlValueGenerationStrategy.IdentityByDefaultColumn),
+                    ItemId = table.Column<long>(type: "bigint", nullable: false),
+                    WarehouseId = table.Column<long>(type: "bigint", nullable: false),
+                    BinId = table.Column<long>(type: "bigint", nullable: true),
+                    BatchId = table.Column<long>(type: "bigint", nullable: true),
+                    SerialId = table.Column<long>(type: "bigint", nullable: true),
+                    UserId = table.Column<long>(type: "bigint", nullable: false),
+                    Direction = table.Column<string>(type: "character varying(5)", maxLength: 5, nullable: false),
+                    QtyBase = table.Column<decimal>(type: "numeric(18,4)", precision: 18, scale: 4, nullable: false),
+                    UnitCost = table.Column<decimal>(type: "numeric(18,6)", precision: 18, scale: 6, nullable: false),
+                    Value = table.Column<decimal>(type: "numeric(18,4)", precision: 18, scale: 4, nullable: false),
+                    RunningBalance = table.Column<decimal>(type: "numeric(18,4)", precision: 18, scale: 4, nullable: false),
+                    SourceDocType = table.Column<string>(type: "character varying(10)", maxLength: 10, nullable: false),
+                    SourceDocId = table.Column<long>(type: "bigint", nullable: false),
+                    CreatedAt = table.Column<DateTime>(type: "timestamp with time zone", nullable: false)
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("PK_stock_ledger", x => x.LedgerId);
+                    table.ForeignKey(
+                        name: "FK_stock_ledger_batches_BatchId",
+                        column: x => x.BatchId,
+                        principalTable: "batches",
+                        principalColumn: "BatchId",
+                        onDelete: ReferentialAction.Restrict);
+                    table.ForeignKey(
+                        name: "FK_stock_ledger_bins_BinId",
+                        column: x => x.BinId,
+                        principalTable: "bins",
+                        principalColumn: "BinId",
+                        onDelete: ReferentialAction.Restrict);
+                    table.ForeignKey(
+                        name: "FK_stock_ledger_items_ItemId",
+                        column: x => x.ItemId,
+                        principalTable: "items",
+                        principalColumn: "ItemId",
+                        onDelete: ReferentialAction.Restrict);
+                    table.ForeignKey(
+                        name: "FK_stock_ledger_serials_SerialId",
+                        column: x => x.SerialId,
+                        principalTable: "serials",
+                        principalColumn: "SerialId",
+                        onDelete: ReferentialAction.Restrict);
+                    table.ForeignKey(
+                        name: "FK_stock_ledger_users_UserId",
+                        column: x => x.UserId,
+                        principalTable: "users",
+                        principalColumn: "UserId",
+                        onDelete: ReferentialAction.Restrict);
+                    table.ForeignKey(
+                        name: "FK_stock_ledger_warehouses_WarehouseId",
+                        column: x => x.WarehouseId,
+                        principalTable: "warehouses",
+                        principalColumn: "WarehouseId",
+                        onDelete: ReferentialAction.Restrict);
+                });
+
+            migrationBuilder.CreateTable(
+                name: "stock_layers",
+                columns: table => new
+                {
+                    LayerId = table.Column<long>(type: "bigint", nullable: false)
+                        .Annotation("Npgsql:ValueGenerationStrategy", NpgsqlValueGenerationStrategy.IdentityByDefaultColumn),
+                    ItemId = table.Column<long>(type: "bigint", nullable: false),
+                    WarehouseId = table.Column<long>(type: "bigint", nullable: false),
+                    BatchId = table.Column<long>(type: "bigint", nullable: true),
+                    SerialId = table.Column<long>(type: "bigint", nullable: true),
+                    GrnLineId = table.Column<long>(type: "bigint", nullable: true),
+                    QtyReceived = table.Column<decimal>(type: "numeric(18,4)", precision: 18, scale: 4, nullable: false),
+                    QtyRemaining = table.Column<decimal>(type: "numeric(18,4)", precision: 18, scale: 4, nullable: false),
+                    UnitCost = table.Column<decimal>(type: "numeric(18,6)", precision: 18, scale: 6, nullable: false),
+                    ReceiptDate = table.Column<DateTime>(type: "timestamp with time zone", nullable: false)
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("PK_stock_layers", x => x.LayerId);
+                    table.ForeignKey(
+                        name: "FK_stock_layers_batches_BatchId",
+                        column: x => x.BatchId,
+                        principalTable: "batches",
+                        principalColumn: "BatchId",
+                        onDelete: ReferentialAction.Restrict);
+                    table.ForeignKey(
+                        name: "FK_stock_layers_grn_lines_GrnLineId",
+                        column: x => x.GrnLineId,
+                        principalTable: "grn_lines",
+                        principalColumn: "GrnLineId",
+                        onDelete: ReferentialAction.Restrict);
+                    table.ForeignKey(
+                        name: "FK_stock_layers_items_ItemId",
+                        column: x => x.ItemId,
+                        principalTable: "items",
+                        principalColumn: "ItemId",
+                        onDelete: ReferentialAction.Restrict);
+                    table.ForeignKey(
+                        name: "FK_stock_layers_serials_SerialId",
+                        column: x => x.SerialId,
+                        principalTable: "serials",
+                        principalColumn: "SerialId",
+                        onDelete: ReferentialAction.Restrict);
+                    table.ForeignKey(
+                        name: "FK_stock_layers_warehouses_WarehouseId",
+                        column: x => x.WarehouseId,
+                        principalTable: "warehouses",
+                        principalColumn: "WarehouseId",
+                        onDelete: ReferentialAction.Restrict);
+                });
+
+            migrationBuilder.CreateIndex(
+                name: "IX_batches_ItemId_BatchNo",
+                table: "batches",
+                columns: new[] { "ItemId", "BatchNo" },
+                unique: true);
+
+            migrationBuilder.CreateIndex(
+                name: "IX_grn_lines_BatchId",
+                table: "grn_lines",
+                column: "BatchId");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_grn_lines_BinId",
+                table: "grn_lines",
+                column: "BinId");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_grn_lines_GrnId",
+                table: "grn_lines",
+                column: "GrnId");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_grn_lines_ItemId",
+                table: "grn_lines",
+                column: "ItemId");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_grn_lines_PoLineId",
+                table: "grn_lines",
+                column: "PoLineId");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_grn_lines_UomId",
+                table: "grn_lines",
+                column: "UomId");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_grns_CreatedBy",
+                table: "grns",
+                column: "CreatedBy");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_grns_DocNo",
+                table: "grns",
+                column: "DocNo",
+                unique: true);
+
+            migrationBuilder.CreateIndex(
+                name: "IX_grns_PoId",
+                table: "grns",
+                column: "PoId");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_grns_Status",
+                table: "grns",
+                column: "Status");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_grns_VendorId",
+                table: "grns",
+                column: "VendorId");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_grns_WarehouseId",
+                table: "grns",
+                column: "WarehouseId");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_serials_ItemId_SerialNo",
+                table: "serials",
+                columns: new[] { "ItemId", "SerialNo" },
+                unique: true);
+
+            migrationBuilder.CreateIndex(
+                name: "IX_stock_layers_BatchId",
+                table: "stock_layers",
+                column: "BatchId");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_stock_layers_GrnLineId",
+                table: "stock_layers",
+                column: "GrnLineId");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_stock_layers_ItemId_WarehouseId_ReceiptDate_LayerId",
+                table: "stock_layers",
+                columns: new[] { "ItemId", "WarehouseId", "ReceiptDate", "LayerId" });
+
+            migrationBuilder.CreateIndex(
+                name: "IX_stock_layers_SerialId",
+                table: "stock_layers",
+                column: "SerialId");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_stock_layers_WarehouseId",
+                table: "stock_layers",
+                column: "WarehouseId");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_stock_ledger_BatchId",
+                table: "stock_ledger",
+                column: "BatchId");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_stock_ledger_BinId",
+                table: "stock_ledger",
+                column: "BinId");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_stock_ledger_ItemId_WarehouseId_CreatedAt",
+                table: "stock_ledger",
+                columns: new[] { "ItemId", "WarehouseId", "CreatedAt" });
+
+            migrationBuilder.CreateIndex(
+                name: "IX_stock_ledger_ItemId_WarehouseId_LedgerId",
+                table: "stock_ledger",
+                columns: new[] { "ItemId", "WarehouseId", "LedgerId" });
+
+            migrationBuilder.CreateIndex(
+                name: "IX_stock_ledger_SerialId",
+                table: "stock_ledger",
+                column: "SerialId");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_stock_ledger_SourceDocType_SourceDocId",
+                table: "stock_ledger",
+                columns: new[] { "SourceDocType", "SourceDocId" });
+
+            migrationBuilder.CreateIndex(
+                name: "IX_stock_ledger_UserId",
+                table: "stock_ledger",
+                column: "UserId");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_stock_ledger_WarehouseId",
+                table: "stock_ledger",
+                column: "WarehouseId");
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropTable(
+                name: "stock_layers");
+
+            migrationBuilder.DropTable(
+                name: "stock_ledger");
+
+            migrationBuilder.DropTable(
+                name: "grn_lines");
+
+            migrationBuilder.DropTable(
+                name: "serials");
+
+            migrationBuilder.DropTable(
+                name: "batches");
+
+            migrationBuilder.DropTable(
+                name: "grns");
+        }
+    }
+}

Backend/ERPCore/Infra/Persistence/Migrations/20260713061141_AddStockTransactions.cs

@@ -0,0 +1,337 @@
+using System;
+using Microsoft.EntityFrameworkCore.Migrations;
+using Npgsql.EntityFrameworkCore.PostgreSQL.Metadata;
+
+#nullable disable
+
+namespace ERPCore.Infra.Persistence.Migrations
+{
+    /// <inheritdoc />
+    public partial class AddStockTransactions : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.CreateTable(
+                name: "reason_codes",
+                columns: table => new
+                {
+                    ReasonCodeId = table.Column<long>(type: "bigint", nullable: false)
+                        .Annotation("Npgsql:ValueGenerationStrategy", NpgsqlValueGenerationStrategy.IdentityByDefaultColumn),
+                    Code = table.Column<string>(type: "character varying(20)", maxLength: 20, nullable: false),
+                    Description = table.Column<string>(type: "character varying(200)", maxLength: 200, nullable: false),
+                    Context = table.Column<string>(type: "character varying(20)", maxLength: 20, nullable: false)
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("PK_reason_codes", x => x.ReasonCodeId);
+                });
+
+            migrationBuilder.CreateTable(
+                name: "stock_transfers",
+                columns: table => new
+                {
+                    TransferId = table.Column<long>(type: "bigint", nullable: false)
+                        .Annotation("Npgsql:ValueGenerationStrategy", NpgsqlValueGenerationStrategy.IdentityByDefaultColumn),
+                    DocNo = table.Column<string>(type: "character varying(30)", maxLength: 30, nullable: false),
+                    SrcWarehouseId = table.Column<long>(type: "bigint", nullable: false),
+                    DestWarehouseId = table.Column<long>(type: "bigint", nullable: false),
+                    Status = table.Column<string>(type: "character varying(20)", maxLength: 20, nullable: false),
+                    CreatedBy = table.Column<long>(type: "bigint", nullable: false),
+                    CreatedAt = table.Column<DateTime>(type: "timestamp with time zone", nullable: false),
+                    xmin = table.Column<uint>(type: "xid", rowVersion: true, nullable: false)
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("PK_stock_transfers", x => x.TransferId);
+                    table.ForeignKey(
+                        name: "FK_stock_transfers_users_CreatedBy",
+                        column: x => x.CreatedBy,
+                        principalTable: "users",
+                        principalColumn: "UserId",
+                        onDelete: ReferentialAction.Restrict);
+                    table.ForeignKey(
+                        name: "FK_stock_transfers_warehouses_DestWarehouseId",
+                        column: x => x.DestWarehouseId,
+                        principalTable: "warehouses",
+                        principalColumn: "WarehouseId",
+                        onDelete: ReferentialAction.Restrict);
+                    table.ForeignKey(
+                        name: "FK_stock_transfers_warehouses_SrcWarehouseId",
+                        column: x => x.SrcWarehouseId,
+                        principalTable: "warehouses",
+                        principalColumn: "WarehouseId",
+                        onDelete: ReferentialAction.Restrict);
+                });
+
+            migrationBuilder.CreateTable(
+                name: "stock_adjustments",
+                columns: table => new
+                {
+                    AdjustmentId = table.Column<long>(type: "bigint", nullable: false)
+                        .Annotation("Npgsql:ValueGenerationStrategy", NpgsqlValueGenerationStrategy.IdentityByDefaultColumn),
+                    DocNo = table.Column<string>(type: "character varying(30)", maxLength: 30, nullable: false),
+                    WarehouseId = table.Column<long>(type: "bigint", nullable: false),
+                    ReasonCodeId = table.Column<long>(type: "bigint", nullable: false),
+                    Status = table.Column<string>(type: "character varying(20)", maxLength: 20, nullable: false),
+                    CreatedBy = table.Column<long>(type: "bigint", nullable: false),
+                    CreatedAt = table.Column<DateTime>(type: "timestamp with time zone", nullable: false),
+                    xmin = table.Column<uint>(type: "xid", rowVersion: true, nullable: false)
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("PK_stock_adjustments", x => x.AdjustmentId);
+                    table.ForeignKey(
+                        name: "FK_stock_adjustments_reason_codes_ReasonCodeId",
+                        column: x => x.ReasonCodeId,
+                        principalTable: "reason_codes",
+                        principalColumn: "ReasonCodeId",
+                        onDelete: ReferentialAction.Restrict);
+                    table.ForeignKey(
+                        name: "FK_stock_adjustments_users_CreatedBy",
+                        column: x => x.CreatedBy,
+                        principalTable: "users",
+                        principalColumn: "UserId",
+                        onDelete: ReferentialAction.Restrict);
+                    table.ForeignKey(
+                        name: "FK_stock_adjustments_warehouses_WarehouseId",
+                        column: x => x.WarehouseId,
+                        principalTable: "warehouses",
+                        principalColumn: "WarehouseId",
+                        onDelete: ReferentialAction.Restrict);
+                });
+
+            migrationBuilder.CreateTable(
+                name: "stock_transfer_lines",
+                columns: table => new
+                {
+                    TransferLineId = table.Column<long>(type: "bigint", nullable: false)
+                        .Annotation("Npgsql:ValueGenerationStrategy", NpgsqlValueGenerationStrategy.IdentityByDefaultColumn),
+                    TransferId = table.Column<long>(type: "bigint", nullable: false),
+                    ItemId = table.Column<long>(type: "bigint", nullable: false),
+                    SrcBinId = table.Column<long>(type: "bigint", nullable: true),
+                    DestBinId = table.Column<long>(type: "bigint", nullable: true),
+                    BatchId = table.Column<long>(type: "bigint", nullable: true),
+                    SerialId = table.Column<long>(type: "bigint", nullable: true),
+                    Qty = table.Column<decimal>(type: "numeric(18,4)", precision: 18, scale: 4, nullable: false),
+                    UnitCost = table.Column<decimal>(type: "numeric(18,6)", precision: 18, scale: 6, nullable: true),
+                    QtyReceived = table.Column<decimal>(type: "numeric(18,4)", precision: 18, scale: 4, nullable: false)
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("PK_stock_transfer_lines", x => x.TransferLineId);
+                    table.ForeignKey(
+                        name: "FK_stock_transfer_lines_batches_BatchId",
+                        column: x => x.BatchId,
+                        principalTable: "batches",
+                        principalColumn: "BatchId",
+                        onDelete: ReferentialAction.Restrict);
+                    table.ForeignKey(
+                        name: "FK_stock_transfer_lines_bins_DestBinId",
+                        column: x => x.DestBinId,
+                        principalTable: "bins",
+                        principalColumn: "BinId",
+                        onDelete: ReferentialAction.Restrict);
+                    table.ForeignKey(
+                        name: "FK_stock_transfer_lines_bins_SrcBinId",
+                        column: x => x.SrcBinId,
+                        principalTable: "bins",
+                        principalColumn: "BinId",
+                        onDelete: ReferentialAction.Restrict);
+                    table.ForeignKey(
+                        name: "FK_stock_transfer_lines_items_ItemId",
+                        column: x => x.ItemId,
+                        principalTable: "items",
+                        principalColumn: "ItemId",
+                        onDelete: ReferentialAction.Restrict);
+                    table.ForeignKey(
+                        name: "FK_stock_transfer_lines_serials_SerialId",
+                        column: x => x.SerialId,
+                        principalTable: "serials",
+                        principalColumn: "SerialId",
+                        onDelete: ReferentialAction.Restrict);
+                    table.ForeignKey(
+                        name: "FK_stock_transfer_lines_stock_transfers_TransferId",
+                        column: x => x.TransferId,
+                        principalTable: "stock_transfers",
+                        principalColumn: "TransferId",
+                        onDelete: ReferentialAction.Cascade);
+                });
+
+            migrationBuilder.CreateTable(
+                name: "stock_adjustment_lines",
+                columns: table => new
+                {
+                    AdjLineId = table.Column<long>(type: "bigint", nullable: false)
+                        .Annotation("Npgsql:ValueGenerationStrategy", NpgsqlValueGenerationStrategy.IdentityByDefaultColumn),
+                    AdjustmentId = table.Column<long>(type: "bigint", nullable: false),
+                    ItemId = table.Column<long>(type: "bigint", nullable: false),
+                    BinId = table.Column<long>(type: "bigint", nullable: true),
+                    BatchId = table.Column<long>(type: "bigint", nullable: true),
+                    SerialId = table.Column<long>(type: "bigint", nullable: true),
+                    QtyDelta = table.Column<decimal>(type: "numeric(18,4)", precision: 18, scale: 4, nullable: false)
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("PK_stock_adjustment_lines", x => x.AdjLineId);
+                    table.ForeignKey(
+                        name: "FK_stock_adjustment_lines_batches_BatchId",
+                        column: x => x.BatchId,
+                        principalTable: "batches",
+                        principalColumn: "BatchId",
+                        onDelete: ReferentialAction.Restrict);
+                    table.ForeignKey(
+                        name: "FK_stock_adjustment_lines_bins_BinId",
+                        column: x => x.BinId,
+                        principalTable: "bins",
+                        principalColumn: "BinId",
+                        onDelete: ReferentialAction.Restrict);
+                    table.ForeignKey(
+                        name: "FK_stock_adjustment_lines_items_ItemId",
+                        column: x => x.ItemId,
+                        principalTable: "items",
+                        principalColumn: "ItemId",
+                        onDelete: ReferentialAction.Restrict);
+                    table.ForeignKey(
+                        name: "FK_stock_adjustment_lines_serials_SerialId",
+                        column: x => x.SerialId,
+                        principalTable: "serials",
+                        principalColumn: "SerialId",
+                        onDelete: ReferentialAction.Restrict);
+                    table.ForeignKey(
+                        name: "FK_stock_adjustment_lines_stock_adjustments_AdjustmentId",
+                        column: x => x.AdjustmentId,
+                        principalTable: "stock_adjustments",
+                        principalColumn: "AdjustmentId",
+                        onDelete: ReferentialAction.Cascade);
+                });
+
+            migrationBuilder.CreateIndex(
+                name: "IX_reason_codes_Context_Code",
+                table: "reason_codes",
+                columns: new[] { "Context", "Code" },
+                unique: true);
+
+            migrationBuilder.CreateIndex(
+                name: "IX_stock_adjustment_lines_AdjustmentId",
+                table: "stock_adjustment_lines",
+                column: "AdjustmentId");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_stock_adjustment_lines_BatchId",
+                table: "stock_adjustment_lines",
+                column: "BatchId");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_stock_adjustment_lines_BinId",
+                table: "stock_adjustment_lines",
+                column: "BinId");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_stock_adjustment_lines_ItemId",
+                table: "stock_adjustment_lines",
+                column: "ItemId");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_stock_adjustment_lines_SerialId",
+                table: "stock_adjustment_lines",
+                column: "SerialId");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_stock_adjustments_CreatedBy",
+                table: "stock_adjustments",
+                column: "CreatedBy");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_stock_adjustments_DocNo",
+                table: "stock_adjustments",
+                column: "DocNo",
+                unique: true);
+
+            migrationBuilder.CreateIndex(
+                name: "IX_stock_adjustments_ReasonCodeId",
+                table: "stock_adjustments",
+                column: "ReasonCodeId");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_stock_adjustments_WarehouseId",
+                table: "stock_adjustments",
+                column: "WarehouseId");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_stock_transfer_lines_BatchId",
+                table: "stock_transfer_lines",
+                column: "BatchId");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_stock_transfer_lines_DestBinId",
+                table: "stock_transfer_lines",
+                column: "DestBinId");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_stock_transfer_lines_ItemId",
+                table: "stock_transfer_lines",
+                column: "ItemId");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_stock_transfer_lines_SerialId",
+                table: "stock_transfer_lines",
+                column: "SerialId");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_stock_transfer_lines_SrcBinId",
+                table: "stock_transfer_lines",
+                column: "SrcBinId");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_stock_transfer_lines_TransferId",
+                table: "stock_transfer_lines",
+                column: "TransferId");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_stock_transfers_CreatedBy",
+                table: "stock_transfers",
+                column: "CreatedBy");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_stock_transfers_DestWarehouseId",
+                table: "stock_transfers",
+                column: "DestWarehouseId");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_stock_transfers_DocNo",
+                table: "stock_transfers",
+                column: "DocNo",
+                unique: true);
+
+            migrationBuilder.CreateIndex(
+                name: "IX_stock_transfers_SrcWarehouseId",
+                table: "stock_transfers",
+                column: "SrcWarehouseId");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_stock_transfers_Status",
+                table: "stock_transfers",
+                column: "Status");
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropTable(
+                name: "stock_adjustment_lines");
+
+            migrationBuilder.DropTable(
+                name: "stock_transfer_lines");
+
+            migrationBuilder.DropTable(
+                name: "stock_adjustments");
+
+            migrationBuilder.DropTable(
+                name: "stock_transfers");
+
+            migrationBuilder.DropTable(
+                name: "reason_codes");
+        }
+    }
+}

Backend/ERPCore/Infra/Persistence/Migrations/20260713105512_AddCountsAndReturns.cs

@@ -0,0 +1,253 @@
+using System;
+using Microsoft.EntityFrameworkCore.Migrations;
+using Npgsql.EntityFrameworkCore.PostgreSQL.Metadata;
+
+#nullable disable
+
+namespace ERPCore.Infra.Persistence.Migrations
+{
+    /// <inheritdoc />
+    public partial class AddCountsAndReturns : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.CreateTable(
+                name: "purchase_returns",
+                columns: table => new
+                {
+                    ReturnId = table.Column<long>(type: "bigint", nullable: false)
+                        .Annotation("Npgsql:ValueGenerationStrategy", NpgsqlValueGenerationStrategy.IdentityByDefaultColumn),
+                    DocNo = table.Column<string>(type: "character varying(30)", maxLength: 30, nullable: false),
+                    VendorId = table.Column<long>(type: "bigint", nullable: false),
+                    WarehouseId = table.Column<long>(type: "bigint", nullable: false),
+                    ReasonCodeId = table.Column<long>(type: "bigint", nullable: false),
+                    Status = table.Column<string>(type: "character varying(20)", maxLength: 20, nullable: false),
+                    CreatedBy = table.Column<long>(type: "bigint", nullable: false),
+                    CreatedAt = table.Column<DateTime>(type: "timestamp with time zone", nullable: false)
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("PK_purchase_returns", x => x.ReturnId);
+                    table.ForeignKey(
+                        name: "FK_purchase_returns_reason_codes_ReasonCodeId",
+                        column: x => x.ReasonCodeId,
+                        principalTable: "reason_codes",
+                        principalColumn: "ReasonCodeId",
+                        onDelete: ReferentialAction.Restrict);
+                    table.ForeignKey(
+                        name: "FK_purchase_returns_users_CreatedBy",
+                        column: x => x.CreatedBy,
+                        principalTable: "users",
+                        principalColumn: "UserId",
+                        onDelete: ReferentialAction.Restrict);
+                    table.ForeignKey(
+                        name: "FK_purchase_returns_vendors_VendorId",
+                        column: x => x.VendorId,
+                        principalTable: "vendors",
+                        principalColumn: "VendorId",
+                        onDelete: ReferentialAction.Restrict);
+                    table.ForeignKey(
+                        name: "FK_purchase_returns_warehouses_WarehouseId",
+                        column: x => x.WarehouseId,
+                        principalTable: "warehouses",
+                        principalColumn: "WarehouseId",
+                        onDelete: ReferentialAction.Restrict);
+                });
+
+            migrationBuilder.CreateTable(
+                name: "stock_counts",
+                columns: table => new
+                {
+                    CountId = table.Column<long>(type: "bigint", nullable: false)
+                        .Annotation("Npgsql:ValueGenerationStrategy", NpgsqlValueGenerationStrategy.IdentityByDefaultColumn),
+                    DocNo = table.Column<string>(type: "character varying(30)", maxLength: 30, nullable: false),
+                    WarehouseId = table.Column<long>(type: "bigint", nullable: false),
+                    CountType = table.Column<string>(type: "character varying(20)", maxLength: 20, nullable: false),
+                    Status = table.Column<string>(type: "character varying(20)", maxLength: 20, nullable: false),
+                    CreatedBy = table.Column<long>(type: "bigint", nullable: false),
+                    CreatedAt = table.Column<DateTime>(type: "timestamp with time zone", nullable: false),
+                    xmin = table.Column<uint>(type: "xid", rowVersion: true, nullable: false)
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("PK_stock_counts", x => x.CountId);
+                    table.ForeignKey(
+                        name: "FK_stock_counts_users_CreatedBy",
+                        column: x => x.CreatedBy,
+                        principalTable: "users",
+                        principalColumn: "UserId",
+                        onDelete: ReferentialAction.Restrict);
+                    table.ForeignKey(
+                        name: "FK_stock_counts_warehouses_WarehouseId",
+                        column: x => x.WarehouseId,
+                        principalTable: "warehouses",
+                        principalColumn: "WarehouseId",
+                        onDelete: ReferentialAction.Restrict);
+                });
+
+            migrationBuilder.CreateTable(
+                name: "purchase_return_lines",
+                columns: table => new
+                {
+                    ReturnLineId = table.Column<long>(type: "bigint", nullable: false)
+                        .Annotation("Npgsql:ValueGenerationStrategy", NpgsqlValueGenerationStrategy.IdentityByDefaultColumn),
+                    ReturnId = table.Column<long>(type: "bigint", nullable: false),
+                    GrnLineId = table.Column<long>(type: "bigint", nullable: true),
+                    ItemId = table.Column<long>(type: "bigint", nullable: false),
+                    Qty = table.Column<decimal>(type: "numeric(18,4)", precision: 18, scale: 4, nullable: false)
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("PK_purchase_return_lines", x => x.ReturnLineId);
+                    table.ForeignKey(
+                        name: "FK_purchase_return_lines_grn_lines_GrnLineId",
+                        column: x => x.GrnLineId,
+                        principalTable: "grn_lines",
+                        principalColumn: "GrnLineId",
+                        onDelete: ReferentialAction.Restrict);
+                    table.ForeignKey(
+                        name: "FK_purchase_return_lines_items_ItemId",
+                        column: x => x.ItemId,
+                        principalTable: "items",
+                        principalColumn: "ItemId",
+                        onDelete: ReferentialAction.Restrict);
+                    table.ForeignKey(
+                        name: "FK_purchase_return_lines_purchase_returns_ReturnId",
+                        column: x => x.ReturnId,
+                        principalTable: "purchase_returns",
+                        principalColumn: "ReturnId",
+                        onDelete: ReferentialAction.Cascade);
+                });
+
+            migrationBuilder.CreateTable(
+                name: "stock_count_lines",
+                columns: table => new
+                {
+                    CountLineId = table.Column<long>(type: "bigint", nullable: false)
+                        .Annotation("Npgsql:ValueGenerationStrategy", NpgsqlValueGenerationStrategy.IdentityByDefaultColumn),
+                    CountId = table.Column<long>(type: "bigint", nullable: false),
+                    ItemId = table.Column<long>(type: "bigint", nullable: false),
+                    BinId = table.Column<long>(type: "bigint", nullable: true),
+                    SystemQty = table.Column<decimal>(type: "numeric(18,4)", precision: 18, scale: 4, nullable: false),
+                    CountedQty = table.Column<decimal>(type: "numeric(18,4)", precision: 18, scale: 4, nullable: true),
+                    Variance = table.Column<decimal>(type: "numeric(18,4)", precision: 18, scale: 4, nullable: true)
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("PK_stock_count_lines", x => x.CountLineId);
+                    table.ForeignKey(
+                        name: "FK_stock_count_lines_bins_BinId",
+                        column: x => x.BinId,
+                        principalTable: "bins",
+                        principalColumn: "BinId",
+                        onDelete: ReferentialAction.Restrict);
+                    table.ForeignKey(
+                        name: "FK_stock_count_lines_items_ItemId",
+                        column: x => x.ItemId,
+                        principalTable: "items",
+                        principalColumn: "ItemId",
+                        onDelete: ReferentialAction.Restrict);
+                    table.ForeignKey(
+                        name: "FK_stock_count_lines_stock_counts_CountId",
+                        column: x => x.CountId,
+                        principalTable: "stock_counts",
+                        principalColumn: "CountId",
+                        onDelete: ReferentialAction.Cascade);
+                });
+
+            migrationBuilder.CreateIndex(
+                name: "IX_purchase_return_lines_GrnLineId",
+                table: "purchase_return_lines",
+                column: "GrnLineId");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_purchase_return_lines_ItemId",
+                table: "purchase_return_lines",
+                column: "ItemId");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_purchase_return_lines_ReturnId",
+                table: "purchase_return_lines",
+                column: "ReturnId");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_purchase_returns_CreatedBy",
+                table: "purchase_returns",
+                column: "CreatedBy");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_purchase_returns_DocNo",
+                table: "purchase_returns",
+                column: "DocNo",
+                unique: true);
+
+            migrationBuilder.CreateIndex(
+                name: "IX_purchase_returns_ReasonCodeId",
+                table: "purchase_returns",
+                column: "ReasonCodeId");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_purchase_returns_VendorId",
+                table: "purchase_returns",
+                column: "VendorId");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_purchase_returns_WarehouseId",
+                table: "purchase_returns",
+                column: "WarehouseId");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_stock_count_lines_BinId",
+                table: "stock_count_lines",
+                column: "BinId");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_stock_count_lines_CountId",
+                table: "stock_count_lines",
+                column: "CountId");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_stock_count_lines_ItemId",
+                table: "stock_count_lines",
+                column: "ItemId");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_stock_counts_CreatedBy",
+                table: "stock_counts",
+                column: "CreatedBy");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_stock_counts_DocNo",
+                table: "stock_counts",
+                column: "DocNo",
+                unique: true);
+
+            migrationBuilder.CreateIndex(
+                name: "IX_stock_counts_Status",
+                table: "stock_counts",
+                column: "Status");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_stock_counts_WarehouseId",
+                table: "stock_counts",
+                column: "WarehouseId");
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropTable(
+                name: "purchase_return_lines");
+
+            migrationBuilder.DropTable(
+                name: "stock_count_lines");
+
+            migrationBuilder.DropTable(
+                name: "purchase_returns");
+
+            migrationBuilder.DropTable(
+                name: "stock_counts");
+        }
+    }
+}

Backend/ERPCore/Infra/Persistence/Migrations/20260713121825_AddAuditAndJournal.cs

@@ -0,0 +1,87 @@
+using System;
+using Microsoft.EntityFrameworkCore.Migrations;
+using Npgsql.EntityFrameworkCore.PostgreSQL.Metadata;
+
+#nullable disable
+
+namespace ERPCore.Infra.Persistence.Migrations
+{
+    /// <inheritdoc />
+    public partial class AddAuditAndJournal : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.CreateTable(
+                name: "audit_logs",
+                columns: table => new
+                {
+                    AuditId = table.Column<long>(type: "bigint", nullable: false)
+                        .Annotation("Npgsql:ValueGenerationStrategy", NpgsqlValueGenerationStrategy.IdentityByDefaultColumn),
+                    UserId = table.Column<long>(type: "bigint", nullable: false),
+                    EntityType = table.Column<string>(type: "character varying(80)", maxLength: 80, nullable: false),
+                    EntityId = table.Column<long>(type: "bigint", nullable: false),
+                    Action = table.Column<string>(type: "character varying(10)", maxLength: 10, nullable: false),
+                    ChangeSet = table.Column<string>(type: "jsonb", nullable: false),
+                    CreatedAt = table.Column<DateTime>(type: "timestamp with time zone", nullable: false)
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("PK_audit_logs", x => x.AuditId);
+                    table.ForeignKey(
+                        name: "FK_audit_logs_users_UserId",
+                        column: x => x.UserId,
+                        principalTable: "users",
+                        principalColumn: "UserId",
+                        onDelete: ReferentialAction.Restrict);
+                });
+
+            migrationBuilder.CreateTable(
+                name: "journal_entry_stubs",
+                columns: table => new
+                {
+                    JournalId = table.Column<long>(type: "bigint", nullable: false)
+                        .Annotation("Npgsql:ValueGenerationStrategy", NpgsqlValueGenerationStrategy.IdentityByDefaultColumn),
+                    SourceDocType = table.Column<string>(type: "character varying(10)", maxLength: 10, nullable: false),
+                    SourceDocId = table.Column<long>(type: "bigint", nullable: false),
+                    DebitAccount = table.Column<string>(type: "character varying(20)", maxLength: 20, nullable: false),
+                    CreditAccount = table.Column<string>(type: "character varying(20)", maxLength: 20, nullable: false),
+                    Amount = table.Column<decimal>(type: "numeric(18,4)", precision: 18, scale: 4, nullable: false)
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("PK_journal_entry_stubs", x => x.JournalId);
+                });
+
+            migrationBuilder.CreateIndex(
+                name: "IX_audit_logs_CreatedAt",
+                table: "audit_logs",
+                column: "CreatedAt");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_audit_logs_EntityType_EntityId",
+                table: "audit_logs",
+                columns: new[] { "EntityType", "EntityId" });
+
+            migrationBuilder.CreateIndex(
+                name: "IX_audit_logs_UserId",
+                table: "audit_logs",
+                column: "UserId");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_journal_entry_stubs_SourceDocType_SourceDocId",
+                table: "journal_entry_stubs",
+                columns: new[] { "SourceDocType", "SourceDocId" });
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropTable(
+                name: "audit_logs");
+
+            migrationBuilder.DropTable(
+                name: "journal_entry_stubs");
+        }
+    }
+}

Backend/ERPCore/Program.cs

@@ -6,6 +6,7 @@ using ERPCore.Repositories;
 using ERPCore.Repositories.Interfaces;
 using ERPCore.Services;
 using ERPCore.Services.Interfaces;
+using ERPCore.Services.Stock;
 using ERPCore.System.Errors;
 using Microsoft.EntityFrameworkCore;
 using Microsoft.OpenApi;
@@ -54,6 +55,23 @@ builder.Services.AddScoped<IRequisitionService, RequisitionService>();
 builder.Services.AddScoped<IRfqService, RfqService>();
 builder.Services.AddScoped<IPurchaseOrderService, PurchaseOrderService>();
 
+// Stock core + goods receipt (docs/11 §4–5)
+builder.Services.AddScoped<IFifoCostingService, FifoCostingService>();
+builder.Services.AddScoped<IStockService, StockService>();
+builder.Services.AddScoped<IGrnService, GrnService>();
+
+// Stock transactions + reference data (docs/11 §5–6)
+builder.Services.AddScoped<IStockMutator, StockMutator>();
+builder.Services.AddScoped<IReasonCodeService, ReasonCodeService>();
+builder.Services.AddScoped<IAdjustmentService, AdjustmentService>();
+builder.Services.AddScoped<ITransferService, TransferService>();
+builder.Services.AddScoped<ICountService, CountService>();
+builder.Services.AddScoped<IReorderService, ReorderService>();
+builder.Services.AddScoped<IPurchaseReturnService, PurchaseReturnService>();
+
+// Cross-cutting: audit trail + GL-ready journal read access (docs/11 §6 / FR-X-02, FR-STK-13)
+builder.Services.AddScoped<IAuditService, AuditService>();
+
 // Health checks (EF Core DB)
 builder.Services.AddHealthChecks().AddDbContextCheck<ErpDbContext>();
 
@@ -63,6 +81,13 @@ builder.Services.AddSwaggerGen(o => o.SwaggerDoc("v1", new OpenApiInfo { Title =
 
 var app = builder.Build();
 
+// Seed configurable reference data (reason codes) idempotently at startup.
+using (var scope = app.Services.CreateScope())
+{
+    var db = scope.ServiceProvider.GetRequiredService<ErpDbContext>();
+    await DataSeeder.SeedAsync(db);
+}
+
 app.UseSerilogRequestLogging();
 
 if (app.Environment.IsDevelopment())

Backend/ERPCore/Services/AdjustmentService.cs

@@ -0,0 +1,104 @@
+using ERPCore.Domain;
+using ERPCore.Domain.Entities;
+using ERPCore.Domain.Enums;
+using ERPCore.Dtos.Stock;
+using ERPCore.Infra.Auth;
+using ERPCore.Infra.UoW;
+using ERPCore.Repositories.Interfaces;
+using ERPCore.Services.Interfaces;
+using ERPCore.System.Errors;
+using Microsoft.EntityFrameworkCore;
+
+namespace ERPCore.Services;
+
+/// <summary>
+/// Stock-adjustment service — the highest-risk feature (02-SECURITY C.5). Auto-posts
+/// with a mandatory reason code and user stamp. Line application (FIFO consume on a
+/// decrease, layer create on an increase) + ledger posting is delegated to
+/// <see cref="IStockMutator"/>. Runs in a single UoW transaction (NFR-02/05).
+/// </summary>
+public sealed class AdjustmentService : IAdjustmentService
+{
+    private readonly IRepository<StockAdjustment> _adjustments;
+    private readonly IRepository<Warehouse> _warehouses;
+    private readonly IRepository<Item> _items;
+    private readonly IRepository<ReasonCode> _reasonCodes;
+    private readonly IStockMutator _mutator;
+    private readonly INumberSequenceService _numbers;
+    private readonly ICurrentUser _currentUser;
+    private readonly IUnitOfWork _uow;
+
+    public AdjustmentService(
+        IRepository<StockAdjustment> adjustments, IRepository<Warehouse> warehouses, IRepository<Item> items,
+        IRepository<ReasonCode> reasonCodes, IStockMutator mutator, INumberSequenceService numbers,
+        ICurrentUser currentUser, IUnitOfWork uow)
+    {
+        _adjustments = adjustments;
+        _warehouses = warehouses;
+        _items = items;
+        _reasonCodes = reasonCodes;
+        _mutator = mutator;
+        _numbers = numbers;
+        _currentUser = currentUser;
+        _uow = uow;
+    }
+
+    public async Task<AdjustmentDto> CreateAsync(CreateAdjustmentRequest request, CancellationToken ct = default)
+    {
+        if (request.ReasonCodeId is null)
+            throw new DomainException(ErrorCodes.ReasonCodeRequired, "A reason code is required for an adjustment.", 400);
+
+        if (!await _warehouses.Query().AnyAsync(w => w.WarehouseId == request.WarehouseId, ct))
+            throw new DomainException(ErrorCodes.Validation, $"Warehouse {request.WarehouseId} does not exist.", 422);
+
+        var reason = await _reasonCodes.Query().AsNoTracking().FirstOrDefaultAsync(r => r.ReasonCodeId == request.ReasonCodeId, ct)
+            ?? throw new DomainException(ErrorCodes.Validation, $"Reason code {request.ReasonCodeId} does not exist.", 422);
+        if (reason.Context != ReasonContext.Adjustment)
+            throw new DomainException(ErrorCodes.Validation, $"Reason code {request.ReasonCodeId} is not an Adjustment reason.", 422);
+
+        foreach (var line in request.Lines)
+        {
+            if (line.QtyDelta == 0)
+                throw new DomainException(ErrorCodes.Validation, "qtyDelta cannot be zero.", 422);
+            if (!await _items.Query().AnyAsync(i => i.ItemId == line.ItemId, ct))
+                throw new DomainException(ErrorCodes.Validation, $"Item {line.ItemId} does not exist.", 422);
+        }
+
+        var now = DateTime.UtcNow;
+        var deltas = request.Lines
+            .Select(l => new StockDelta(l.ItemId, l.BinId, l.BatchId, l.QtyDelta)).ToList();
+
+        var (adjustment, ledgerRefs) = await _uow.ExecuteInTransactionAsync(async token =>
+        {
+            var docNo = await _numbers.NextAsync(DocumentTypes.Adjustment, token);
+            var entity = new StockAdjustment
+            {
+                DocNo = docNo,
+                WarehouseId = request.WarehouseId,
+                ReasonCodeId = request.ReasonCodeId.Value,
+                Status = AdjustmentStatus.Posted,
+                CreatedBy = _currentUser.AuditUserId,
+                CreatedAt = now,
+                Lines = request.Lines.Select(l => new StockAdjustmentLine
+                {
+                    ItemId = l.ItemId,
+                    BinId = l.BinId,
+                    BatchId = l.BatchId,
+                    QtyDelta = l.QtyDelta
+                }).ToList()
+            };
+            await _adjustments.AddAsync(entity, token);
+            await _uow.SaveChangesAsync(token); // flush so AdjustmentId is a valid ledger sourceDocId
+
+            var refs = await _mutator.ApplyAsync(request.WarehouseId, DocumentTypes.Adjustment, entity.AdjustmentId, now, deltas, token);
+            return (entity, refs);
+        }, ct);
+
+        return new AdjustmentDto(
+            adjustment.AdjustmentId, adjustment.DocNo, adjustment.WarehouseId, adjustment.ReasonCodeId,
+            adjustment.Status, adjustment.CreatedBy, adjustment.CreatedAt,
+            adjustment.Lines.OrderBy(l => l.AdjLineId)
+                .Select(l => new AdjustmentLineDto(l.AdjLineId, l.ItemId, l.BinId, l.BatchId, l.QtyDelta)).ToList(),
+            ledgerRefs.Select(l => l.LedgerId).ToList());
+    }
+}

Backend/ERPCore/Services/AuditService.cs

@@ -0,0 +1,58 @@
+using System.Text.Json;
+using ERPCore.Domain.Entities;
+using ERPCore.Dtos.Audit;
+using ERPCore.Dtos.Common;
+using ERPCore.Repositories.Interfaces;
+using ERPCore.Services.Interfaces;
+using Microsoft.EntityFrameworkCore;
+
+namespace ERPCore.Services;
+
+public sealed class AuditService : IAuditService
+{
+    private readonly IRepository<AuditLog> _logs;
+    private readonly IRepository<JournalEntryStub> _journal;
+
+    public AuditService(IRepository<AuditLog> logs, IRepository<JournalEntryStub> journal)
+    {
+        _logs = logs;
+        _journal = journal;
+    }
+
+    public async Task<PagedResponse<AuditLogDto>> ListLogsAsync(
+        string? entityType, long? entityId, long? userId, DateOnly? from, DateOnly? to, PageQuery query, CancellationToken ct = default)
+    {
+        var q = _logs.Query().AsNoTracking();
+        if (!string.IsNullOrWhiteSpace(entityType)) q = q.Where(l => l.EntityType == entityType);
+        if (entityId is not null) q = q.Where(l => l.EntityId == entityId);
+        if (userId is not null) q = q.Where(l => l.UserId == userId);
+        if (from is not null) q = q.Where(l => l.CreatedAt >= from.Value.ToDateTime(TimeOnly.MinValue));
+        if (to is not null) q = q.Where(l => l.CreatedAt < to.Value.AddDays(1).ToDateTime(TimeOnly.MinValue));
+
+        var total = await q.CountAsync(ct);
+        var rows = await q.OrderByDescending(l => l.AuditId)
+            .Skip(query.Skip).Take(query.PageSize).ToListAsync(ct);
+
+        var dtos = rows.Select(l => new AuditLogDto(
+            l.AuditId, l.UserId, l.EntityType, l.EntityId, l.Action,
+            JsonSerializer.Deserialize<JsonElement>(l.ChangeSet), l.CreatedAt)).ToList();
+
+        return PagedResponse<AuditLogDto>.Create(dtos, query.Page, query.PageSize, total);
+    }
+
+    public async Task<PagedResponse<JournalEntryStubDto>> ListJournalAsync(
+        string? sourceDocType, long? sourceDocId, PageQuery query, CancellationToken ct = default)
+    {
+        var q = _journal.Query().AsNoTracking();
+        if (!string.IsNullOrWhiteSpace(sourceDocType)) q = q.Where(j => j.SourceDocType == sourceDocType);
+        if (sourceDocId is not null) q = q.Where(j => j.SourceDocId == sourceDocId);
+
+        var total = await q.CountAsync(ct);
+        var rows = await q.OrderByDescending(j => j.JournalId)
+            .Skip(query.Skip).Take(query.PageSize)
+            .Select(j => new JournalEntryStubDto(j.JournalId, j.SourceDocType, j.SourceDocId, j.DebitAccount, j.CreditAccount, j.Amount))
+            .ToListAsync(ct);
+
+        return PagedResponse<JournalEntryStubDto>.Create(rows, query.Page, query.PageSize, total);
+    }
+}

Backend/ERPCore/Services/CountService.cs

@@ -0,0 +1,181 @@
+using ERPCore.Domain;
+using ERPCore.Domain.Entities;
+using ERPCore.Domain.Enums;
+using ERPCore.Dtos.Stock;
+using ERPCore.Infra.Auth;
+using ERPCore.Infra.UoW;
+using ERPCore.Repositories.Interfaces;
+using ERPCore.Services.Interfaces;
+using ERPCore.System.Errors;
+using Microsoft.EntityFrameworkCore;
+
+namespace ERPCore.Services;
+
+/// <summary>
+/// Stock-count service (FR-STK-08). Create snapshots system quantities (immutable,
+/// 02-SECURITY C.7); posting emits a variance <see cref="StockAdjustment"/> via the
+/// shared <see cref="IStockMutator"/> (a variance is an adjustment in disguise, C.7)
+/// and closes the count — all in one UoW transaction.
+/// </summary>
+public sealed class CountService : ICountService
+{
+    private const string VarianceReasonCode = "VAR";
+
+    private readonly IRepository<StockCount> _counts;
+    private readonly IRepository<StockAdjustment> _adjustments;
+    private readonly IRepository<Warehouse> _warehouses;
+    private readonly IRepository<Item> _items;
+    private readonly IRepository<ReasonCode> _reasonCodes;
+    private readonly IFifoCostingService _fifo;
+    private readonly IStockMutator _mutator;
+    private readonly INumberSequenceService _numbers;
+    private readonly ICurrentUser _currentUser;
+    private readonly IUnitOfWork _uow;
+
+    public CountService(
+        IRepository<StockCount> counts, IRepository<StockAdjustment> adjustments, IRepository<Warehouse> warehouses,
+        IRepository<Item> items, IRepository<ReasonCode> reasonCodes, IFifoCostingService fifo, IStockMutator mutator,
+        INumberSequenceService numbers, ICurrentUser currentUser, IUnitOfWork uow)
+    {
+        _counts = counts;
+        _adjustments = adjustments;
+        _warehouses = warehouses;
+        _items = items;
+        _reasonCodes = reasonCodes;
+        _fifo = fifo;
+        _mutator = mutator;
+        _numbers = numbers;
+        _currentUser = currentUser;
+        _uow = uow;
+    }
+
+    public async Task<CountDto?> GetAsync(long countId, CancellationToken ct = default)
+    {
+        var count = await _counts.Query().AsNoTracking().Include(c => c.Lines)
+            .FirstOrDefaultAsync(c => c.CountId == countId, ct);
+        return count is null ? null : Map(count);
+    }
+
+    public async Task<CountDto> CreateAsync(CreateCountRequest request, CancellationToken ct = default)
+    {
+        if (!await _warehouses.Query().AnyAsync(w => w.WarehouseId == request.WarehouseId, ct))
+            throw new DomainException(ErrorCodes.Validation, $"Warehouse {request.WarehouseId} does not exist.", 422);
+
+        var itemIds = request.ItemIds.Distinct().ToList();
+        foreach (var id in itemIds)
+            if (!await _items.Query().AnyAsync(i => i.ItemId == id, ct))
+                throw new DomainException(ErrorCodes.Validation, $"Item {id} does not exist.", 422);
+
+        // Snapshot system quantities now (immutable once opened).
+        var lines = new List<StockCountLine>();
+        foreach (var id in itemIds)
+        {
+            var systemQty = await _fifo.GetOnHandAsync(id, request.WarehouseId, ct);
+            lines.Add(new StockCountLine { ItemId = id, SystemQty = systemQty });
+        }
+
+        var count = await _uow.ExecuteInTransactionAsync(async token =>
+        {
+            var docNo = await _numbers.NextAsync(DocumentTypes.Count, token);
+            var entity = new StockCount
+            {
+                DocNo = docNo,
+                WarehouseId = request.WarehouseId,
+                CountType = request.CountType,
+                Status = CountStatus.Draft,
+                CreatedBy = _currentUser.AuditUserId,
+                CreatedAt = DateTime.UtcNow,
+                Lines = lines
+            };
+            await _counts.AddAsync(entity, token);
+            return entity;
+        }, ct);
+
+        return Map(count);
+    }
+
+    public async Task<CountDto> EnterCountsAsync(long countId, EnterCountsRequest request, CancellationToken ct = default)
+    {
+        var count = await _counts.Query().Include(c => c.Lines)
+            .FirstOrDefaultAsync(c => c.CountId == countId, ct)
+            ?? throw new NotFoundException($"Count {countId} was not found.");
+        if (count.Status == CountStatus.Posted)
+            throw new ConflictException($"Count {countId} is already posted.");
+
+        foreach (var input in request.Lines)
+        {
+            var line = count.Lines.FirstOrDefault(l => l.CountLineId == input.CountLineId)
+                ?? throw new DomainException(ErrorCodes.Validation, $"Count line {input.CountLineId} is not on count {countId}.", 422);
+            line.CountedQty = input.CountedQty;
+            line.Variance = input.CountedQty - line.SystemQty;
+        }
+
+        count.Status = CountStatus.Counted;
+        await _uow.SaveChangesAsync(ct);
+        return Map(count);
+    }
+
+    public async Task<CountPostResultDto> PostAsync(long countId, CancellationToken ct = default)
+    {
+        var count = await _counts.Query().Include(c => c.Lines)
+            .FirstOrDefaultAsync(c => c.CountId == countId, ct)
+            ?? throw new NotFoundException($"Count {countId} was not found.");
+        if (count.Status == CountStatus.Posted)
+            throw new ConflictException($"Count {countId} is already posted.");
+        if (count.Status != CountStatus.Counted)
+            throw new ConflictException($"Count {countId} has no entered counts to post.");
+
+        var deltas = count.Lines
+            .Where(l => l.Variance.HasValue && l.Variance.Value != 0)
+            .Select(l => new StockDelta(l.ItemId, l.BinId, null, l.Variance!.Value))
+            .ToList();
+
+        // No variances → just close the count, no adjustment.
+        if (deltas.Count == 0)
+        {
+            count.Status = CountStatus.Posted;
+            await _uow.SaveChangesAsync(ct);
+            return new CountPostResultDto(count.CountId, count.Status, null, Array.Empty<long>());
+        }
+
+        var reason = await _reasonCodes.Query().AsNoTracking()
+            .FirstOrDefaultAsync(r => r.Context == ReasonContext.Adjustment && r.Code == VarianceReasonCode, ct)
+            ?? throw new DomainException(ErrorCodes.Validation, $"Reason code '{VarianceReasonCode}' (Count Variance) is not configured.", 422);
+
+        var now = DateTime.UtcNow;
+        var (adjustmentId, ledgerEntries) = await _uow.ExecuteInTransactionAsync(async token =>
+        {
+            var docNo = await _numbers.NextAsync(DocumentTypes.Adjustment, token);
+            var adjustment = new StockAdjustment
+            {
+                DocNo = docNo,
+                WarehouseId = count.WarehouseId,
+                ReasonCodeId = reason.ReasonCodeId,
+                Status = AdjustmentStatus.Posted,
+                CreatedBy = _currentUser.AuditUserId,
+                CreatedAt = now,
+                Lines = deltas.Select(d => new StockAdjustmentLine
+                {
+                    ItemId = d.ItemId,
+                    BinId = d.BinId,
+                    QtyDelta = d.QtyDelta
+                }).ToList()
+            };
+            await _adjustments.AddAsync(adjustment, token);
+            await _uow.SaveChangesAsync(token); // flush for a valid ledger sourceDocId
+
+            var refs = await _mutator.ApplyAsync(count.WarehouseId, DocumentTypes.Adjustment, adjustment.AdjustmentId, now, deltas, token);
+
+            count.Status = CountStatus.Posted;
+            return (adjustment.AdjustmentId, refs);
+        }, ct);
+
+        // Map ledger ids after commit so they are populated.
+        return new CountPostResultDto(count.CountId, count.Status, adjustmentId, ledgerEntries.Select(r => r.LedgerId).ToList());
+    }
+
+    private static CountDto Map(StockCount c) => new(
+        c.CountId, c.DocNo, c.WarehouseId, c.CountType, c.Status,
+        c.Lines.OrderBy(l => l.CountLineId)
+            .Select(l => new CountLineDto(l.CountLineId, l.ItemId, l.BinId, l.SystemQty, l.CountedQty, l.Variance)).ToList());
+}

Backend/ERPCore/Services/GrnService.cs

@@ -0,0 +1,357 @@
+using ERPCore.Domain;
+using ERPCore.Domain.Entities;
+using ERPCore.Domain.Enums;
+using ERPCore.Dtos.Grn;
+using ERPCore.Infra.Auth;
+using ERPCore.Infra.UoW;
+using ERPCore.Repositories.Interfaces;
+using ERPCore.Services.Interfaces;
+using ERPCore.System.Errors;
+using Microsoft.EntityFrameworkCore;
+
+namespace ERPCore.Services;
+
+/// <summary>
+/// Goods-receipt service. Create builds a Draft GRN (cost derived from the PO line
+/// for PO-based receipts — 02-SECURITY C.3; over-receipt tolerance enforced).
+/// Confirm posts FIFO layers + inbound ledger and updates PO receipts inside one
+/// UoW transaction (NFR-02/05). Quantities are converted to the item's base UOM
+/// for the ledger/layers (FR-MD-03).
+/// </summary>
+public sealed class GrnService : IGrnService
+{
+    // Phase 1: block any receipt beyond the PO line's open quantity (configurable later, NFR-10).
+    private const decimal OverReceiptTolerance = 0m;
+
+    private readonly IRepository<Grn> _grns;
+    private readonly IRepository<PurchaseOrder> _pos;
+    private readonly IRepository<PoLine> _poLines;
+    private readonly IRepository<Item> _items;
+    private readonly IRepository<Uom> _uoms;
+    private readonly IRepository<Warehouse> _warehouses;
+    private readonly IRepository<Bin> _bins;
+    private readonly IRepository<Vendor> _vendors;
+    private readonly IRepository<Batch> _batches;
+    private readonly IRepository<UomConversion> _conversions;
+    private readonly IRepository<StockLayer> _layers;
+    private readonly IRepository<StockLedger> _ledger;
+    private readonly IFifoCostingService _fifo;
+    private readonly INumberSequenceService _numbers;
+    private readonly ICurrentUser _currentUser;
+    private readonly IUnitOfWork _uow;
+
+    public GrnService(
+        IRepository<Grn> grns, IRepository<PurchaseOrder> pos, IRepository<PoLine> poLines,
+        IRepository<Item> items, IRepository<Uom> uoms, IRepository<Warehouse> warehouses,
+        IRepository<Bin> bins, IRepository<Vendor> vendors, IRepository<Batch> batches,
+        IRepository<UomConversion> conversions, IRepository<StockLayer> layers, IRepository<StockLedger> ledger,
+        IFifoCostingService fifo, INumberSequenceService numbers, ICurrentUser currentUser, IUnitOfWork uow)
+    {
+        _grns = grns;
+        _pos = pos;
+        _poLines = poLines;
+        _items = items;
+        _uoms = uoms;
+        _warehouses = warehouses;
+        _bins = bins;
+        _vendors = vendors;
+        _batches = batches;
+        _conversions = conversions;
+        _layers = layers;
+        _ledger = ledger;
+        _fifo = fifo;
+        _numbers = numbers;
+        _currentUser = currentUser;
+        _uow = uow;
+    }
+
+    public async Task<GrnDto?> GetAsync(long grnId, CancellationToken ct = default)
+    {
+        var grn = await _grns.Query().AsNoTracking()
+            .Include(g => g.Lines)
+            .FirstOrDefaultAsync(g => g.GrnId == grnId, ct);
+        return grn is null ? null : Map(grn);
+    }
+
+    public async Task<GrnDto> CreateAsync(CreateGrnRequest request, CancellationToken ct = default)
+    {
+        if (!await _warehouses.Query().AnyAsync(w => w.WarehouseId == request.WarehouseId, ct))
+            throw new DomainException(ErrorCodes.Validation, $"Warehouse {request.WarehouseId} does not exist.", 422);
+
+        // Resolve vendor + PO context.
+        PurchaseOrder? po = null;
+        long vendorId;
+        if (request.PoId is not null)
+        {
+            po = await _pos.Query().AsNoTracking().Include(p => p.Lines)
+                .FirstOrDefaultAsync(p => p.PoId == request.PoId, ct)
+                ?? throw new DomainException(ErrorCodes.Validation, $"Purchase order {request.PoId} does not exist.", 422);
+            if (po.Status is not (PurchaseOrderStatus.Approved or PurchaseOrderStatus.PartiallyReceived))
+                throw new ConflictException($"Purchase order {po.PoId} is {po.Status} and cannot be received against.");
+            vendorId = po.VendorId;
+        }
+        else
+        {
+            if (request.VendorId is null)
+                throw new DomainException(ErrorCodes.Validation, "vendorId is required for a direct (no-PO) receipt.", 422);
+            if (!await _vendors.Query().AnyAsync(v => v.VendorId == request.VendorId, ct))
+                throw new DomainException(ErrorCodes.Validation, $"Vendor {request.VendorId} does not exist.", 422);
+            vendorId = request.VendorId.Value;
+        }
+
+        var lines = new List<GrnLine>();
+        var batchCache = new Dictionary<(long ItemId, string BatchNo), Batch>();
+
+        foreach (var input in request.Lines)
+        {
+            var item = await _items.Query().AsNoTracking().FirstOrDefaultAsync(i => i.ItemId == input.ItemId, ct)
+                ?? throw new DomainException(ErrorCodes.Validation, $"Item {input.ItemId} does not exist.", 422);
+            if (!await _uoms.Query().AnyAsync(u => u.UomId == input.UomId, ct))
+                throw new DomainException(ErrorCodes.Validation, $"UOM {input.UomId} does not exist.", 422);
+            if (input.BinId is not null && !await _bins.Query().AnyAsync(b => b.BinId == input.BinId && b.WarehouseId == request.WarehouseId, ct))
+                throw new DomainException(ErrorCodes.Validation, $"Bin {input.BinId} is not in warehouse {request.WarehouseId}.", 422);
+
+            // Cost: PO-derived for PO lines (client cost ignored, C.3); entered for direct.
+            decimal unitCost;
+            if (input.PoLineId is not null)
+            {
+                var poLine = po?.Lines.FirstOrDefault(l => l.PoLineId == input.PoLineId)
+                    ?? throw new DomainException(ErrorCodes.Validation, $"PO line {input.PoLineId} is not on purchase order {request.PoId}.", 422);
+                if (poLine.ItemId != input.ItemId)
+                    throw new DomainException(ErrorCodes.Validation, $"PO line {input.PoLineId} is for a different item.", 422);
+
+                var openQty = poLine.Qty - poLine.QtyReceived;
+                if (input.Qty > openQty * (1 + OverReceiptTolerance))
+                    throw new DomainException(ErrorCodes.OverReceiptTolerance,
+                        $"Receiving {input.Qty} exceeds the open quantity {openQty} on PO line {input.PoLineId}.", 422);
+
+                unitCost = poLine.UnitPrice;
+            }
+            else
+            {
+                unitCost = input.UnitCost;
+            }
+
+            var batch = await ResolveBatchAsync(item, input.Batch, batchCache, ct);
+
+            lines.Add(new GrnLine
+            {
+                PoLineId = input.PoLineId,
+                ItemId = input.ItemId,
+                UomId = input.UomId,
+                BinId = input.BinId,
+                Batch = batch, // navigation so EF fixes up BatchId once the batch is inserted
+                Qty = input.Qty,
+                UnitCost = unitCost,
+                ReceivedValue = Math.Round(input.Qty * unitCost, 4, MidpointRounding.AwayFromZero),
+                HoldStatus = input.HoldStatus
+            });
+        }
+
+        var grn = await _uow.ExecuteInTransactionAsync(async token =>
+        {
+            var docNo = await _numbers.NextAsync(DocumentTypes.Grn, token);
+            var entity = new Grn
+            {
+                DocNo = docNo,
+                PoId = request.PoId,
+                VendorId = vendorId,
+                WarehouseId = request.WarehouseId,
+                Status = GrnStatus.Draft,
+                CreatedBy = _currentUser.AuditUserId,
+                CreatedAt = DateTime.UtcNow,
+                Lines = lines
+            };
+            await _grns.AddAsync(entity, token);
+            return entity;
+        }, ct);
+
+        return Map(grn);
+    }
+
+    public async Task<GrnConfirmResultDto> ConfirmAsync(long grnId, string? idempotencyKey, CancellationToken ct = default)
+    {
+        var grn = await _grns.Query()
+            .Include(g => g.Lines)
+            .FirstOrDefaultAsync(g => g.GrnId == grnId, ct)
+            ?? throw new NotFoundException($"GRN {grnId} was not found.");
+
+        // Idempotent replay: an already-confirmed GRN returns its existing result.
+        if (grn.Status == GrnStatus.Confirmed)
+            return await BuildConfirmResultAsync(grn, ct);
+        if (grn.Status == GrnStatus.Closed)
+            throw new ConflictException($"GRN {grnId} is closed.");
+
+        var actor = _currentUser.AuditUserId;
+        var now = DateTime.UtcNow;
+        var runningBalance = new Dictionary<(long, long), decimal>();
+        var createdLayers = new List<StockLayer>();
+        var ledgerRefs = new List<StockLedger>();
+
+        await _uow.ExecuteInTransactionAsync(async token =>
+        {
+            foreach (var line in grn.Lines.OrderBy(l => l.GrnLineId))
+            {
+                var item = await _items.Query().AsNoTracking().FirstAsync(i => i.ItemId == line.ItemId, token);
+                var (qtyBase, unitCostBase) = await ToBaseAsync(item, line.UomId, line.Qty, line.UnitCost, token);
+
+                var layer = await _fifo.CreateInboundLayerAsync(
+                    line.ItemId, grn.WarehouseId, line.BatchId, null, line.GrnLineId,
+                    qtyBase, unitCostBase, now, token);
+                createdLayers.Add(layer);
+
+                var key = (line.ItemId, grn.WarehouseId);
+                if (!runningBalance.TryGetValue(key, out var bal))
+                    bal = await _fifo.GetOnHandAsync(line.ItemId, grn.WarehouseId, token);
+                bal += qtyBase;
+                runningBalance[key] = bal;
+
+                var entry = await _fifo.PostLedgerAsync(
+                    line.ItemId, grn.WarehouseId, line.BinId, line.BatchId, null, actor,
+                    Direction.In, qtyBase, unitCostBase, bal, DocumentTypes.Grn, grn.GrnId, now, token);
+                ledgerRefs.Add(entry);
+
+                if (line.PoLineId is not null)
+                {
+                    var poLine = await _poLines.GetByIdAsync(line.PoLineId.Value, token);
+                    if (poLine is not null) poLine.QtyReceived += line.Qty;
+                }
+            }
+
+            grn.Status = GrnStatus.Confirmed;
+            grn.PostedAt = now;
+
+            await UpdatePoStatusAsync(grn.PoId, token);
+            return 0;
+        }, ct);
+
+        return new GrnConfirmResultDto(
+            grn.GrnId, grn.Status, now,
+            createdLayers.Select(ToCreatedLayer).ToList(),
+            ledgerRefs.Select(l => l.LedgerId).ToList(),
+            await GetPoStatusAsync(grn.PoId, ct));
+    }
+
+    public async Task<ReleaseLineResultDto> ReleaseLineAsync(long grnId, long grnLineId, string action, CancellationToken ct = default)
+    {
+        var grn = await _grns.Query()
+            .Include(g => g.Lines)
+            .FirstOrDefaultAsync(g => g.GrnId == grnId, ct)
+            ?? throw new NotFoundException($"GRN {grnId} was not found.");
+
+        var line = grn.Lines.FirstOrDefault(l => l.GrnLineId == grnLineId)
+            ?? throw new NotFoundException($"GRN line {grnLineId} was not found on GRN {grnId}.");
+
+        if (grn.Status != GrnStatus.Confirmed)
+            throw new ConflictException($"GRN {grnId} must be confirmed before releasing holds.");
+        if (line.HoldStatus != HoldStatus.OnHold)
+            throw new ConflictException($"GRN line {grnLineId} is {line.HoldStatus}, not OnHold.");
+
+        if (string.Equals(action, "Release", StringComparison.OrdinalIgnoreCase))
+        {
+            line.HoldStatus = HoldStatus.Available;
+            await _uow.SaveChangesAsync(ct);
+            return new ReleaseLineResultDto(grnLineId, HoldStatus.Available);
+        }
+
+        // Reject: remove the held stock from on-hand and post a reversing ledger entry.
+        // Linking rejected stock to a formal purchase return is deferred (§3.4).
+        var actor = _currentUser.AuditUserId;
+        var now = DateTime.UtcNow;
+        await _uow.ExecuteInTransactionAsync(async token =>
+        {
+            line.HoldStatus = HoldStatus.Rejected;
+            var layers = await _layers.Query()
+                .Where(l => l.GrnLineId == grnLineId && l.QtyRemaining > 0).ToListAsync(token);
+
+            foreach (var layer in layers)
+            {
+                var bal = await _fifo.GetOnHandAsync(layer.ItemId, layer.WarehouseId, token) - layer.QtyRemaining;
+                await _fifo.PostLedgerAsync(
+                    layer.ItemId, layer.WarehouseId, line.BinId, layer.BatchId, null, actor,
+                    Direction.Out, layer.QtyRemaining, layer.UnitCost, bal, DocumentTypes.Grn, grn.GrnId, now, token);
+                layer.QtyRemaining = 0;
+            }
+            return 0;
+        }, ct);
+
+        return new ReleaseLineResultDto(grnLineId, HoldStatus.Rejected);
+    }
+
+    private async Task<Batch?> ResolveBatchAsync(
+        Item item, BatchInput? batch, Dictionary<(long, string), Batch> cache, CancellationToken ct)
+    {
+        if (item.TrackingMode == TrackingMode.Batch && batch is null)
+            throw new DomainException(ErrorCodes.Validation, $"Item {item.ItemId} is batch-tracked; a batch is required.", 422);
+        if (batch is null) return null;
+
+        var key = (item.ItemId, batch.BatchNo.Trim());
+        if (cache.TryGetValue(key, out var cached)) return cached;
+
+        var existing = await _batches.Query().FirstOrDefaultAsync(b => b.ItemId == item.ItemId && b.BatchNo == key.Item2, ct);
+        if (existing is not null)
+        {
+            cache[key] = existing;
+            return existing;
+        }
+
+        var created = new Batch { ItemId = item.ItemId, BatchNo = key.Item2, ExpiryDate = batch.ExpiryDate };
+        await _batches.AddAsync(created, ct);
+        cache[key] = created;
+        return created; // linked via GrnLine.Batch navigation; FK fixed up on SaveChanges
+    }
+
+    private async Task<(decimal QtyBase, decimal UnitCostBase)> ToBaseAsync(
+        Item item, long uomId, decimal qty, decimal unitCostPerUom, CancellationToken ct)
+    {
+        if (uomId == item.BaseUomId)
+            return (qty, unitCostPerUom);
+
+        var conv = await _conversions.Query().AsNoTracking()
+            .FirstOrDefaultAsync(c => c.ItemId == item.ItemId && c.FromUomId == uomId && c.ToUomId == item.BaseUomId, ct)
+            ?? throw new DomainException(ErrorCodes.Validation,
+                $"No UOM conversion from {uomId} to base UOM {item.BaseUomId} for item {item.ItemId}.", 422);
+
+        return (qty * conv.Factor, unitCostPerUom / conv.Factor);
+    }
+
+    private async Task UpdatePoStatusAsync(long? poId, CancellationToken ct)
+    {
+        if (poId is null) return;
+        var po = await _pos.Query().Include(p => p.Lines).FirstOrDefaultAsync(p => p.PoId == poId, ct);
+        if (po is null) return;
+
+        po.Status = po.Lines.All(l => l.QtyReceived >= l.Qty)
+            ? PurchaseOrderStatus.FullyReceived
+            : PurchaseOrderStatus.PartiallyReceived;
+        po.UpdatedAt = DateTime.UtcNow;
+    }
+
+    private async Task<PurchaseOrderStatus?> GetPoStatusAsync(long? poId, CancellationToken ct)
+    {
+        if (poId is null) return null;
+        return await _pos.Query().AsNoTracking().Where(p => p.PoId == poId).Select(p => (PurchaseOrderStatus?)p.Status).FirstOrDefaultAsync(ct);
+    }
+
+    private async Task<GrnConfirmResultDto> BuildConfirmResultAsync(Grn grn, CancellationToken ct)
+    {
+        var lineIds = grn.Lines.Select(l => l.GrnLineId).ToList();
+        var layers = await _layers.Query().AsNoTracking()
+            .Where(l => l.GrnLineId != null && lineIds.Contains(l.GrnLineId.Value)).ToListAsync(ct);
+        var ledgerRefs = await _ledger.Query().AsNoTracking()
+            .Where(l => l.SourceDocType == DocumentTypes.Grn && l.SourceDocId == grn.GrnId && l.Direction == Direction.In)
+            .Select(l => l.LedgerId).ToListAsync(ct);
+
+        return new GrnConfirmResultDto(
+            grn.GrnId, grn.Status, grn.PostedAt ?? grn.CreatedAt,
+            layers.Select(ToCreatedLayer).ToList(), ledgerRefs, await GetPoStatusAsync(grn.PoId, ct));
+    }
+
+    private static CreatedLayerDto ToCreatedLayer(StockLayer l) => new(
+        l.LayerId, l.ItemId, l.WarehouseId, l.BatchId, l.QtyReceived, l.QtyRemaining, l.UnitCost, l.ReceiptDate);
+
+    private static GrnDto Map(Grn g) => new(
+        g.GrnId, g.DocNo, g.PoId, g.VendorId, g.WarehouseId, g.Status, g.CreatedBy, g.CreatedAt, g.PostedAt,
+        g.Lines.OrderBy(l => l.GrnLineId).Select(l => new GrnLineDto(
+            l.GrnLineId, l.PoLineId, l.ItemId, l.UomId, l.BinId, l.Qty, l.UnitCost, l.ReceivedValue, l.HoldStatus, l.BatchId)).ToList());
+}

Backend/ERPCore/Services/Interfaces/IAdjustmentService.cs

@@ -0,0 +1,9 @@
+using ERPCore.Dtos.Stock;
+
+namespace ERPCore.Services.Interfaces;
+
+/// <summary>Stock-adjustment business logic (docs/11 §5.5; FR-STK-07; 02-SECURITY C.5).</summary>
+public interface IAdjustmentService
+{
+    Task<AdjustmentDto> CreateAsync(CreateAdjustmentRequest request, CancellationToken ct = default);
+}

Backend/ERPCore/Services/Interfaces/IAuditService.cs

@@ -0,0 +1,17 @@
+using ERPCore.Dtos.Audit;
+using ERPCore.Dtos.Common;
+
+namespace ERPCore.Services.Interfaces;
+
+/// <summary>
+/// Read access to the audit trail and GL-ready journal stubs (auditor role,
+/// 02-SECURITY B.2.3). Both are append-only; no write API.
+/// </summary>
+public interface IAuditService
+{
+    Task<PagedResponse<AuditLogDto>> ListLogsAsync(
+        string? entityType, long? entityId, long? userId, DateOnly? from, DateOnly? to, PageQuery query, CancellationToken ct = default);
+
+    Task<PagedResponse<JournalEntryStubDto>> ListJournalAsync(
+        string? sourceDocType, long? sourceDocId, PageQuery query, CancellationToken ct = default);
+}

Backend/ERPCore/Services/Interfaces/ICountService.cs

@@ -0,0 +1,12 @@
+using ERPCore.Dtos.Stock;
+
+namespace ERPCore.Services.Interfaces;
+
+/// <summary>Cycle/full stock-count business logic (docs/11 §5.6; FR-STK-08).</summary>
+public interface ICountService
+{
+    Task<CountDto?> GetAsync(long countId, CancellationToken ct = default);
+    Task<CountDto> CreateAsync(CreateCountRequest request, CancellationToken ct = default);
+    Task<CountDto> EnterCountsAsync(long countId, EnterCountsRequest request, CancellationToken ct = default);
+    Task<CountPostResultDto> PostAsync(long countId, CancellationToken ct = default);
+}

Backend/ERPCore/Services/Interfaces/IFifoCostingService.cs

@@ -0,0 +1,46 @@
+using ERPCore.Domain.Entities;
+using ERPCore.Domain.Enums;
+using ERPCore.Dtos.Stock;
+
+namespace ERPCore.Services.Interfaces;
+
+/// <summary>
+/// FIFO cost-layer and ledger domain service (00-CORE §4, docs/10 Part A.2).
+/// Invoked by stock services **inside** a UoW transaction — never from a
+/// controller/repository. This turn covers inbound layer creation, ledger posting
+/// and valuation; oldest-first consumption (issues/transfers/adjustments) arrives
+/// with §5 and must row-lock the layers it consumes (NFR-02).
+/// </summary>
+public interface IFifoCostingService
+{
+    /// <summary>Create an inbound FIFO layer (qty and unit cost in the item's base UOM).</summary>
+    Task<StockLayer> CreateInboundLayerAsync(
+        long itemId, long warehouseId, long? batchId, long? serialId, long? grnLineId,
+        decimal qtyBase, decimal unitCost, DateTime receiptDate, CancellationToken ct = default);
+
+    /// <summary>
+    /// Consume <paramref name="qtyBase"/> from open layers oldest-first, row-locking
+    /// the affected layers for the transaction (NFR-02). Skips on-hold and expired
+    /// stock. Throws <c>STOCK_NEGATIVE_BLOCKED</c> if issuable stock is insufficient,
+    /// <c>EXPIRED_BATCH_BLOCKED</c>/<c>ONHOLD_NOT_ISSUABLE</c> for an explicit batch
+    /// that is expired/held. Returns the consumed segments (for cost-preserving moves
+    /// and ledger costing). Must run inside a UoW transaction.
+    /// </summary>
+    Task<IReadOnlyList<ConsumedSegment>> ConsumeAsync(
+        long itemId, long warehouseId, long? batchId, decimal qtyBase, CancellationToken ct = default);
+
+    /// <summary>Append an immutable ledger entry (value = qtyBase × unitCost).</summary>
+    Task<StockLedger> PostLedgerAsync(
+        long itemId, long warehouseId, long? binId, long? batchId, long? serialId, long userId,
+        Direction direction, decimal qtyBase, decimal unitCost, decimal runningBalance,
+        string sourceDocType, long sourceDocId, DateTime createdAt, CancellationToken ct = default);
+
+    /// <summary>Current on-hand (Σ open-layer qtyRemaining) for an item at a warehouse.</summary>
+    Task<decimal> GetOnHandAsync(long itemId, long warehouseId, CancellationToken ct = default);
+
+    /// <summary>Valuation over open layers: Σ(qtyRemaining × unitCost) (FR-STK-04).</summary>
+    Task<StockValuationDto> GetValuationAsync(long itemId, long warehouseId, CancellationToken ct = default);
+}
+
+/// <summary>A quantity consumed from one FIFO layer at that layer's unit cost.</summary>
+public sealed record ConsumedSegment(long LayerId, decimal Qty, decimal UnitCost);

Backend/ERPCore/Services/Interfaces/IGrnService.cs

@@ -0,0 +1,15 @@
+using ERPCore.Dtos.Grn;
+
+namespace ERPCore.Services.Interfaces;
+
+/// <summary>Goods-receipt business logic (docs/11 §4; FR-GRN-01..08).</summary>
+public interface IGrnService
+{
+    Task<GrnDto?> GetAsync(long grnId, CancellationToken ct = default);
+    Task<GrnDto> CreateAsync(CreateGrnRequest request, CancellationToken ct = default);
+
+    /// <summary>Confirm: create FIFO layers + inbound ledger + update PO receipts, atomically.</summary>
+    Task<GrnConfirmResultDto> ConfirmAsync(long grnId, string? idempotencyKey, CancellationToken ct = default);
+
+    Task<ReleaseLineResultDto> ReleaseLineAsync(long grnId, long grnLineId, string action, CancellationToken ct = default);
+}

Backend/ERPCore/Services/Interfaces/IPurchaseReturnService.cs

@@ -0,0 +1,9 @@
+using ERPCore.Dtos.Procurement;
+
+namespace ERPCore.Services.Interfaces;
+
+/// <summary>Purchase-return business logic (docs/11 §3.4; FR-PROC-08).</summary>
+public interface IPurchaseReturnService
+{
+    Task<PurchaseReturnDto> CreateAsync(CreatePurchaseReturnRequest request, CancellationToken ct = default);
+}

Backend/ERPCore/Services/Interfaces/IReasonCodeService.cs

@@ -0,0 +1,12 @@
+using ERPCore.Domain.Enums;
+using ERPCore.Dtos.Common;
+using ERPCore.Dtos.Reference;
+
+namespace ERPCore.Services.Interfaces;
+
+/// <summary>Reason-code reference data (docs/11 §6; FR-X-04).</summary>
+public interface IReasonCodeService
+{
+    Task<PagedResponse<ReasonCodeDto>> ListAsync(ReasonContext? context, PageQuery query, CancellationToken ct = default);
+    Task<ReasonCodeDto> CreateAsync(CreateReasonCodeRequest request, CancellationToken ct = default);
+}

Backend/ERPCore/Services/Interfaces/IReorderService.cs

@@ -0,0 +1,12 @@
+using ERPCore.Dtos.Common;
+using ERPCore.Dtos.Procurement;
+using ERPCore.Dtos.Stock;
+
+namespace ERPCore.Services.Interfaces;
+
+/// <summary>Reorder alerts and suggested requisitions (docs/11 §5.7; FR-STK-10).</summary>
+public interface IReorderService
+{
+    Task<PagedResponse<ReorderAlertDto>> GetAlertsAsync(long? warehouseId, PageQuery query, CancellationToken ct = default);
+    Task<RequisitionDto> CreateSuggestedRequisitionAsync(long itemId, long warehouseId, CancellationToken ct = default);
+}

Backend/ERPCore/Services/Interfaces/IStockMutator.cs

@@ -0,0 +1,21 @@
+using ERPCore.Domain.Entities;
+
+namespace ERPCore.Services.Interfaces;
+
+/// <summary>A signed base-UOM change to an item's stock at one warehouse.</summary>
+public sealed record StockDelta(long ItemId, long? BinId, long? BatchId, decimal QtyDelta);
+
+/// <summary>
+/// Shared poster for stock-affecting documents (adjustments, count variances,
+/// purchase returns). Applies signed deltas — negative consumes FIFO layers
+/// oldest-first (row-locked, negative-stock blocked), positive creates a layer at
+/// last cost — and appends the ledger entries. Runs inside the caller's UoW
+/// transaction (the caller owns numbering, the header, and the commit); the
+/// document must already be saved so its id is a valid ledger <c>sourceDocId</c>.
+/// </summary>
+public interface IStockMutator
+{
+    Task<IReadOnlyList<StockLedger>> ApplyAsync(
+        long warehouseId, string sourceDocType, long sourceDocId, DateTime now,
+        IReadOnlyList<StockDelta> deltas, CancellationToken ct = default);
+}

Backend/ERPCore/Services/Interfaces/IStockService.cs

@@ -0,0 +1,15 @@
+using ERPCore.Dtos.Common;
+using ERPCore.Dtos.Stock;
+
+namespace ERPCore.Services.Interfaces;
+
+/// <summary>Read-side stock enquiry, ledger and valuation (docs/11 §5.1–5.3).</summary>
+public interface IStockService
+{
+    Task<StockOnHandDto> GetOnHandAsync(long itemId, long warehouseId, CancellationToken ct = default);
+
+    Task<PagedResponse<StockLedgerRowDto>> GetLedgerAsync(
+        long? itemId, long? warehouseId, DateOnly? from, DateOnly? to, PageQuery query, CancellationToken ct = default);
+
+    Task<StockValuationDto> GetValuationAsync(long itemId, long warehouseId, CancellationToken ct = default);
+}

Backend/ERPCore/Services/Interfaces/ITransferService.cs

@@ -0,0 +1,16 @@
+using ERPCore.Dtos.Stock;
+
+namespace ERPCore.Services.Interfaces;
+
+/// <summary>Inter-warehouse transfer business logic (docs/11 §5.4; FR-STK-05/06).</summary>
+public interface ITransferService
+{
+    Task<TransferDto?> GetAsync(long transferId, CancellationToken ct = default);
+    Task<TransferDto> CreateAsync(CreateTransferRequest request, CancellationToken ct = default);
+
+    /// <summary>Dispatch: consume source FIFO layers into in-transit (row-locked).</summary>
+    Task<DispatchResultDto> DispatchAsync(long transferId, CancellationToken ct = default);
+
+    /// <summary>Receive: create the destination layer at the inherited (cost-preserving) cost.</summary>
+    Task<ReceiveResultDto> ReceiveAsync(long transferId, ReceiveTransferRequest request, CancellationToken ct = default);
+}

Backend/ERPCore/Services/PurchaseReturnService.cs

@@ -0,0 +1,115 @@
+using ERPCore.Domain;
+using ERPCore.Domain.Entities;
+using ERPCore.Domain.Enums;
+using ERPCore.Dtos.Procurement;
+using ERPCore.Infra.Auth;
+using ERPCore.Infra.UoW;
+using ERPCore.Repositories.Interfaces;
+using ERPCore.Services.Interfaces;
+using ERPCore.System.Errors;
+using Microsoft.EntityFrameworkCore;
+
+namespace ERPCore.Services;
+
+/// <summary>
+/// Purchase-return service (FR-PROC-08). Auto-posts with a mandatory Return reason
+/// code and generates an outbound stock movement via the shared
+/// <see cref="IStockMutator"/> (FIFO consume, row-locked; over-return beyond
+/// available → STOCK_NEGATIVE_BLOCKED). Single UoW transaction.
+/// </summary>
+public sealed class PurchaseReturnService : IPurchaseReturnService
+{
+    private readonly IRepository<PurchaseReturn> _returns;
+    private readonly IRepository<Vendor> _vendors;
+    private readonly IRepository<Warehouse> _warehouses;
+    private readonly IRepository<Item> _items;
+    private readonly IRepository<ReasonCode> _reasonCodes;
+    private readonly IRepository<GrnLine> _grnLines;
+    private readonly IStockMutator _mutator;
+    private readonly INumberSequenceService _numbers;
+    private readonly ICurrentUser _currentUser;
+    private readonly IUnitOfWork _uow;
+
+    public PurchaseReturnService(
+        IRepository<PurchaseReturn> returns, IRepository<Vendor> vendors, IRepository<Warehouse> warehouses,
+        IRepository<Item> items, IRepository<ReasonCode> reasonCodes, IRepository<GrnLine> grnLines,
+        IStockMutator mutator, INumberSequenceService numbers, ICurrentUser currentUser, IUnitOfWork uow)
+    {
+        _returns = returns;
+        _vendors = vendors;
+        _warehouses = warehouses;
+        _items = items;
+        _reasonCodes = reasonCodes;
+        _grnLines = grnLines;
+        _mutator = mutator;
+        _numbers = numbers;
+        _currentUser = currentUser;
+        _uow = uow;
+    }
+
+    public async Task<PurchaseReturnDto> CreateAsync(CreatePurchaseReturnRequest request, CancellationToken ct = default)
+    {
+        if (request.ReasonCodeId is null)
+            throw new DomainException(ErrorCodes.ReasonCodeRequired, "A reason code is required for a purchase return.", 400);
+
+        if (!await _vendors.Query().AnyAsync(v => v.VendorId == request.VendorId, ct))
+            throw new DomainException(ErrorCodes.Validation, $"Vendor {request.VendorId} does not exist.", 422);
+        if (!await _warehouses.Query().AnyAsync(w => w.WarehouseId == request.WarehouseId, ct))
+            throw new DomainException(ErrorCodes.Validation, $"Warehouse {request.WarehouseId} does not exist.", 422);
+
+        var reason = await _reasonCodes.Query().AsNoTracking().FirstOrDefaultAsync(r => r.ReasonCodeId == request.ReasonCodeId, ct)
+            ?? throw new DomainException(ErrorCodes.Validation, $"Reason code {request.ReasonCodeId} does not exist.", 422);
+        if (reason.Context != ReasonContext.Return)
+            throw new DomainException(ErrorCodes.Validation, $"Reason code {request.ReasonCodeId} is not a Return reason.", 422);
+
+        foreach (var line in request.Lines)
+        {
+            if (!await _items.Query().AnyAsync(i => i.ItemId == line.ItemId, ct))
+                throw new DomainException(ErrorCodes.Validation, $"Item {line.ItemId} does not exist.", 422);
+            if (line.GrnLineId is not null)
+            {
+                var grnLine = await _grnLines.Query().AsNoTracking().FirstOrDefaultAsync(g => g.GrnLineId == line.GrnLineId, ct)
+                    ?? throw new DomainException(ErrorCodes.Validation, $"GRN line {line.GrnLineId} does not exist.", 422);
+                if (grnLine.ItemId != line.ItemId)
+                    throw new DomainException(ErrorCodes.Validation, $"GRN line {line.GrnLineId} is for a different item.", 422);
+            }
+        }
+
+        var now = DateTime.UtcNow;
+        var deltas = request.Lines.Select(l => new StockDelta(l.ItemId, null, null, -l.Qty)).ToList();
+
+        var (entity, ledgerEntries) = await _uow.ExecuteInTransactionAsync(async token =>
+        {
+            var docNo = await _numbers.NextAsync(DocumentTypes.PurchaseReturn, token);
+            var ret = new PurchaseReturn
+            {
+                DocNo = docNo,
+                VendorId = request.VendorId,
+                WarehouseId = request.WarehouseId,
+                ReasonCodeId = request.ReasonCodeId.Value,
+                Status = ReturnStatus.Posted,
+                CreatedBy = _currentUser.AuditUserId,
+                CreatedAt = now,
+                Lines = request.Lines.Select(l => new PurchaseReturnLine
+                {
+                    GrnLineId = l.GrnLineId,
+                    ItemId = l.ItemId,
+                    Qty = l.Qty
+                }).ToList()
+            };
+            await _returns.AddAsync(ret, token);
+            await _uow.SaveChangesAsync(token); // flush for a valid ledger sourceDocId
+
+            var refs = await _mutator.ApplyAsync(request.WarehouseId, DocumentTypes.PurchaseReturn, ret.ReturnId, now, deltas, token);
+            return (ret, refs);
+        }, ct);
+
+        // Map ledger ids after commit so they are populated.
+        return new PurchaseReturnDto(
+            entity.ReturnId, entity.DocNo, entity.VendorId, entity.WarehouseId, entity.ReasonCodeId, entity.Status,
+            entity.CreatedBy,
+            entity.Lines.OrderBy(l => l.ReturnLineId)
+                .Select(l => new PurchaseReturnLineDto(l.ReturnLineId, l.GrnLineId, l.ItemId, l.Qty)).ToList(),
+            ledgerEntries.Select(r => r.LedgerId).ToList());
+    }
+}

Backend/ERPCore/Services/ReasonCodeService.cs

@@ -0,0 +1,50 @@
+using ERPCore.Domain.Entities;
+using ERPCore.Domain.Enums;
+using ERPCore.Dtos.Common;
+using ERPCore.Dtos.Reference;
+using ERPCore.Infra.UoW;
+using ERPCore.Repositories.Interfaces;
+using ERPCore.Services.Interfaces;
+using ERPCore.System.Errors;
+using Microsoft.EntityFrameworkCore;
+
+namespace ERPCore.Services;
+
+public sealed class ReasonCodeService : IReasonCodeService
+{
+    private readonly IRepository<ReasonCode> _codes;
+    private readonly IUnitOfWork _uow;
+
+    public ReasonCodeService(IRepository<ReasonCode> codes, IUnitOfWork uow)
+    {
+        _codes = codes;
+        _uow = uow;
+    }
+
+    public async Task<PagedResponse<ReasonCodeDto>> ListAsync(ReasonContext? context, PageQuery query, CancellationToken ct = default)
+    {
+        var q = _codes.Query().AsNoTracking();
+        if (context is not null) q = q.Where(r => r.Context == context);
+
+        var total = await q.CountAsync(ct);
+        var rows = await q.OrderBy(r => r.Context).ThenBy(r => r.Code)
+            .Skip(query.Skip).Take(query.PageSize)
+            .Select(r => new ReasonCodeDto(r.ReasonCodeId, r.Code, r.Description, r.Context))
+            .ToListAsync(ct);
+
+        return PagedResponse<ReasonCodeDto>.Create(rows, query.Page, query.PageSize, total);
+    }
+
+    public async Task<ReasonCodeDto> CreateAsync(CreateReasonCodeRequest request, CancellationToken ct = default)
+    {
+        var code = request.Code.Trim().ToUpperInvariant();
+        if (await _codes.Query().AnyAsync(r => r.Context == request.Context && r.Code == code, ct))
+            throw new ConflictException($"Reason code '{code}' already exists in context {request.Context}.");
+
+        var entity = new ReasonCode { Code = code, Description = request.Description.Trim(), Context = request.Context };
+        await _codes.AddAsync(entity, ct);
+        await _uow.SaveChangesAsync(ct);
+
+        return new ReasonCodeDto(entity.ReasonCodeId, entity.Code, entity.Description, entity.Context);
+    }
+}

Backend/ERPCore/Services/ReorderService.cs

@@ -0,0 +1,59 @@
+using ERPCore.Domain.Entities;
+using ERPCore.Dtos.Common;
+using ERPCore.Dtos.Procurement;
+using ERPCore.Dtos.Stock;
+using ERPCore.Repositories.Interfaces;
+using ERPCore.Services.Interfaces;
+using ERPCore.System.Errors;
+using Microsoft.EntityFrameworkCore;
+
+namespace ERPCore.Services;
+
+/// <summary>
+/// Reorder alerts are a query, not a stored entity (docs/10 C.9): available stock
+/// (from the FIFO layers) is compared to <see cref="ItemReorder"/> policy on read.
+/// </summary>
+public sealed class ReorderService : IReorderService
+{
+    private readonly IRepository<ItemReorder> _reorders;
+    private readonly IStockService _stock;
+    private readonly IRequisitionService _requisitions;
+
+    public ReorderService(IRepository<ItemReorder> reorders, IStockService stock, IRequisitionService requisitions)
+    {
+        _reorders = reorders;
+        _stock = stock;
+        _requisitions = requisitions;
+    }
+
+    public async Task<PagedResponse<ReorderAlertDto>> GetAlertsAsync(long? warehouseId, PageQuery query, CancellationToken ct = default)
+    {
+        var q = _reorders.Query().AsNoTracking();
+        if (warehouseId is not null) q = q.Where(r => r.WarehouseId == warehouseId);
+        var policies = await q.OrderBy(r => r.ItemId).ToListAsync(ct);
+
+        var alerts = new List<ReorderAlertDto>();
+        foreach (var p in policies)
+        {
+            var available = (await _stock.GetOnHandAsync(p.ItemId, p.WarehouseId, ct)).Available;
+            if (available <= p.ReorderPoint)
+                alerts.Add(new ReorderAlertDto(p.ItemId, p.WarehouseId, available, p.ReorderPoint, p.ReorderQty, p.ReorderQty));
+        }
+
+        var page = alerts.Skip(query.Skip).Take(query.PageSize).ToList();
+        return PagedResponse<ReorderAlertDto>.Create(page, query.Page, query.PageSize, alerts.Count);
+    }
+
+    public async Task<RequisitionDto> CreateSuggestedRequisitionAsync(long itemId, long warehouseId, CancellationToken ct = default)
+    {
+        var policy = await _reorders.Query().AsNoTracking()
+            .FirstOrDefaultAsync(r => r.ItemId == itemId && r.WarehouseId == warehouseId, ct)
+            ?? throw new DomainException(ErrorCodes.Validation,
+                $"No reorder policy for item {itemId} at warehouse {warehouseId}.", 422);
+
+        return await _requisitions.CreateAsync(new CreateRequisitionRequest
+        {
+            Lines = [new CreateRequisitionLineInput { ItemId = itemId, Qty = policy.ReorderQty }]
+        }, ct);
+    }
+}

Backend/ERPCore/Services/Stock/FifoCostingService.cs

@@ -0,0 +1,183 @@
+using ERPCore.Domain.Entities;
+using ERPCore.Domain.Enums;
+using ERPCore.Dtos.Stock;
+using ERPCore.Infra.Persistence;
+using ERPCore.Repositories.Interfaces;
+using ERPCore.Services.Interfaces;
+using ERPCore.System.Errors;
+using Microsoft.EntityFrameworkCore;
+
+namespace ERPCore.Services.Stock;
+
+/// <summary>
+/// FIFO cost-layer + ledger writer and valuation reader (docs/10 Part A.2).
+/// Writes (layer/ledger creation) are added to the tracked context and persisted
+/// by the caller's UoW transaction; they are never saved here.
+/// </summary>
+public sealed class FifoCostingService : IFifoCostingService
+{
+    public const string BaseCurrency = "LKR";
+    public const string Method = "FIFO";
+
+    // Phase-1 placeholder GL accounts (data only, no posting — FR-STK-13).
+    private const string InventoryAccount = "1300";
+    private const string ClearingAccount = "2100";
+
+    private readonly IRepository<StockLayer> _layers;
+    private readonly IRepository<StockLedger> _ledger;
+    private readonly IRepository<JournalEntryStub> _journal;
+    private readonly ErpDbContext _db;
+
+    public FifoCostingService(
+        IRepository<StockLayer> layers, IRepository<StockLedger> ledger,
+        IRepository<JournalEntryStub> journal, ErpDbContext db)
+    {
+        _layers = layers;
+        _ledger = ledger;
+        _journal = journal;
+        _db = db;
+    }
+
+    public async Task<StockLayer> CreateInboundLayerAsync(
+        long itemId, long warehouseId, long? batchId, long? serialId, long? grnLineId,
+        decimal qtyBase, decimal unitCost, DateTime receiptDate, CancellationToken ct = default)
+    {
+        var layer = new StockLayer
+        {
+            ItemId = itemId,
+            WarehouseId = warehouseId,
+            BatchId = batchId,
+            SerialId = serialId,
+            GrnLineId = grnLineId,
+            QtyReceived = qtyBase,
+            QtyRemaining = qtyBase,
+            UnitCost = unitCost,
+            ReceiptDate = receiptDate
+        };
+        await _layers.AddAsync(layer, ct);
+        return layer;
+    }
+
+    public async Task<IReadOnlyList<ConsumedSegment>> ConsumeAsync(
+        long itemId, long warehouseId, long? batchId, decimal qtyBase, CancellationToken ct = default)
+    {
+        var today = DateOnly.FromDateTime(DateTime.UtcNow);
+
+        if (batchId is not null)
+        {
+            var expiry = await _db.Batches.AsNoTracking()
+                .Where(b => b.BatchId == batchId).Select(b => b.ExpiryDate).FirstOrDefaultAsync(ct);
+            if (expiry is not null && expiry < today)
+                throw new DomainException(ErrorCodes.ExpiredBatchBlocked,
+                    $"Batch {batchId} expired on {expiry:yyyy-MM-dd} and cannot be issued.", 409);
+        }
+
+        // Row-lock the issuable open layers oldest-first (SELECT … FOR UPDATE, NFR-02).
+        // Excludes on-hold (grn line) and expired-batch stock. No LINQ is composed on
+        // top of the raw SQL so the FOR UPDATE reaches the database intact.
+        // {batchId}::bigint casts give Npgsql an explicit type for the (possibly null)
+        // parameter — without it a null batch filter fails with 42P18.
+        var layers = await _db.StockLayers
+            .FromSqlInterpolated($"""
+                SELECT * FROM stock_layers sl
+                WHERE sl."ItemId" = {itemId} AND sl."WarehouseId" = {warehouseId} AND sl."QtyRemaining" > 0
+                  AND ({batchId}::bigint IS NULL OR sl."BatchId" = {batchId}::bigint)
+                  AND NOT EXISTS (SELECT 1 FROM grn_lines gl WHERE gl."GrnLineId" = sl."GrnLineId" AND gl."HoldStatus" = 'OnHold')
+                  AND NOT EXISTS (SELECT 1 FROM batches b WHERE b."BatchId" = sl."BatchId" AND b."ExpiryDate" < {today})
+                ORDER BY sl."ReceiptDate", sl."LayerId"
+                FOR UPDATE
+                """)
+            .ToListAsync(ct);
+
+        var available = layers.Sum(l => l.QtyRemaining);
+        if (available < qtyBase)
+        {
+            var heldExists = await _db.StockLayers.AsNoTracking().AnyAsync(l =>
+                l.ItemId == itemId && l.WarehouseId == warehouseId && l.QtyRemaining > 0
+                && (batchId == null || l.BatchId == batchId)
+                && l.GrnLine != null && l.GrnLine.HoldStatus == HoldStatus.OnHold, ct);
+            if (heldExists)
+                throw new DomainException(ErrorCodes.OnHoldNotIssuable,
+                    $"Stock for item {itemId} at warehouse {warehouseId} is on inspection hold and cannot be issued.", 409);
+
+            throw new DomainException(ErrorCodes.StockNegativeBlocked,
+                $"Available {available} < requested {qtyBase} for item {itemId} at warehouse {warehouseId}.", 409);
+        }
+
+        var segments = new List<ConsumedSegment>();
+        var remaining = qtyBase;
+        foreach (var layer in layers)
+        {
+            if (remaining <= 0) break;
+            var take = Math.Min(remaining, layer.QtyRemaining);
+            layer.QtyRemaining -= take;
+            remaining -= take;
+            segments.Add(new ConsumedSegment(layer.LayerId, take, layer.UnitCost));
+        }
+
+        return segments;
+    }
+
+    public async Task<StockLedger> PostLedgerAsync(
+        long itemId, long warehouseId, long? binId, long? batchId, long? serialId, long userId,
+        Direction direction, decimal qtyBase, decimal unitCost, decimal runningBalance,
+        string sourceDocType, long sourceDocId, DateTime createdAt, CancellationToken ct = default)
+    {
+        var entry = new StockLedger
+        {
+            ItemId = itemId,
+            WarehouseId = warehouseId,
+            BinId = binId,
+            BatchId = batchId,
+            SerialId = serialId,
+            UserId = userId,
+            Direction = direction,
+            QtyBase = qtyBase,
+            UnitCost = unitCost,
+            Value = Math.Round(qtyBase * unitCost, 4, MidpointRounding.AwayFromZero),
+            RunningBalance = runningBalance,
+            SourceDocType = sourceDocType,
+            SourceDocId = sourceDocId,
+            CreatedAt = createdAt
+        };
+        await _ledger.AddAsync(entry, ct);
+
+        // GL-ready journal entry per movement (FR-STK-13; data only, no posting).
+        // Inbound debits Inventory / credits Clearing; outbound reverses.
+        var (debit, credit) = direction == Direction.In
+            ? (InventoryAccount, ClearingAccount)
+            : (ClearingAccount, InventoryAccount);
+        await _journal.AddAsync(new JournalEntryStub
+        {
+            SourceDocType = sourceDocType,
+            SourceDocId = sourceDocId,
+            DebitAccount = debit,
+            CreditAccount = credit,
+            Amount = entry.Value
+        }, ct);
+
+        return entry;
+    }
+
+    public async Task<decimal> GetOnHandAsync(long itemId, long warehouseId, CancellationToken ct = default)
+        => await _layers.Query().AsNoTracking()
+            .Where(l => l.ItemId == itemId && l.WarehouseId == warehouseId)
+            .SumAsync(l => (decimal?)l.QtyRemaining, ct) ?? 0m;
+
+    public async Task<StockValuationDto> GetValuationAsync(long itemId, long warehouseId, CancellationToken ct = default)
+    {
+        var open = await _layers.Query().AsNoTracking()
+            .Where(l => l.ItemId == itemId && l.WarehouseId == warehouseId && l.QtyRemaining > 0)
+            .OrderBy(l => l.ReceiptDate).ThenBy(l => l.LayerId)
+            .Select(l => new { l.LayerId, l.QtyRemaining, l.UnitCost, l.ReceiptDate })
+            .ToListAsync(ct);
+
+        var layers = open.Select(l => new StockValuationLayerDto(
+            l.LayerId, l.QtyRemaining, l.UnitCost,
+            Math.Round(l.QtyRemaining * l.UnitCost, 4, MidpointRounding.AwayFromZero), l.ReceiptDate)).ToList();
+
+        return new StockValuationDto(
+            itemId, warehouseId, layers,
+            layers.Sum(l => l.QtyRemaining), layers.Sum(l => l.Value), BaseCurrency, Method);
+    }
+}

Backend/ERPCore/Services/Stock/StockMutator.cs

@@ -0,0 +1,77 @@
+using ERPCore.Domain.Entities;
+using ERPCore.Domain.Enums;
+using ERPCore.Infra.Auth;
+using ERPCore.Repositories.Interfaces;
+using ERPCore.Services.Interfaces;
+using Microsoft.EntityFrameworkCore;
+
+namespace ERPCore.Services.Stock;
+
+/// <summary>
+/// Applies signed stock deltas for a document and posts the ledger (see
+/// <see cref="IStockMutator"/>). Running balances are tracked in-memory per
+/// (item, warehouse), seeded from current on-hand, so multiple lines for the same
+/// item chain correctly within the transaction.
+/// </summary>
+public sealed class StockMutator : IStockMutator
+{
+    private readonly IFifoCostingService _fifo;
+    private readonly IRepository<StockLayer> _layers;
+    private readonly ICurrentUser _currentUser;
+
+    public StockMutator(IFifoCostingService fifo, IRepository<StockLayer> layers, ICurrentUser currentUser)
+    {
+        _fifo = fifo;
+        _layers = layers;
+        _currentUser = currentUser;
+    }
+
+    public async Task<IReadOnlyList<StockLedger>> ApplyAsync(
+        long warehouseId, string sourceDocType, long sourceDocId, DateTime now,
+        IReadOnlyList<StockDelta> deltas, CancellationToken ct = default)
+    {
+        var actor = _currentUser.AuditUserId;
+        var balances = new Dictionary<long, decimal>();
+        var entries = new List<StockLedger>();
+
+        foreach (var d in deltas)
+        {
+            if (d.QtyDelta == 0) continue;
+
+            if (!balances.TryGetValue(d.ItemId, out var bal))
+                bal = await _fifo.GetOnHandAsync(d.ItemId, warehouseId, ct);
+
+            StockLedger entry;
+            if (d.QtyDelta < 0)
+            {
+                var qty = -d.QtyDelta;
+                var segments = await _fifo.ConsumeAsync(d.ItemId, warehouseId, d.BatchId, qty, ct);
+                var unitCost = segments.Sum(s => s.Qty * s.UnitCost) / qty;
+                bal -= qty;
+                entry = await _fifo.PostLedgerAsync(
+                    d.ItemId, warehouseId, d.BinId, d.BatchId, null, actor,
+                    Direction.Out, qty, unitCost, bal, sourceDocType, sourceDocId, now, ct);
+            }
+            else
+            {
+                var unitCost = await LastCostAsync(d.ItemId, warehouseId, ct);
+                await _fifo.CreateInboundLayerAsync(d.ItemId, warehouseId, d.BatchId, null, null, d.QtyDelta, unitCost, now, ct);
+                bal += d.QtyDelta;
+                entry = await _fifo.PostLedgerAsync(
+                    d.ItemId, warehouseId, d.BinId, d.BatchId, null, actor,
+                    Direction.In, d.QtyDelta, unitCost, bal, sourceDocType, sourceDocId, now, ct);
+            }
+
+            balances[d.ItemId] = bal;
+            entries.Add(entry);
+        }
+
+        return entries;
+    }
+
+    private async Task<decimal> LastCostAsync(long itemId, long warehouseId, CancellationToken ct)
+        => await _layers.Query().AsNoTracking()
+            .Where(l => l.ItemId == itemId && l.WarehouseId == warehouseId)
+            .OrderByDescending(l => l.ReceiptDate).ThenByDescending(l => l.LayerId)
+            .Select(l => (decimal?)l.UnitCost).FirstOrDefaultAsync(ct) ?? 0m;
+}

Backend/ERPCore/Services/Stock/StockService.cs

@@ -0,0 +1,76 @@
+using ERPCore.Domain.Entities;
+using ERPCore.Domain.Enums;
+using ERPCore.Dtos.Common;
+using ERPCore.Dtos.Stock;
+using ERPCore.Repositories.Interfaces;
+using ERPCore.Services.Interfaces;
+using Microsoft.EntityFrameworkCore;
+
+namespace ERPCore.Services.Stock;
+
+public sealed class StockService : IStockService
+{
+    private readonly IFifoCostingService _fifo;
+    private readonly IRepository<StockLayer> _layers;
+    private readonly IRepository<StockLedger> _ledger;
+    private readonly IRepository<StockTransferLine> _transferLines;
+
+    public StockService(
+        IFifoCostingService fifo, IRepository<StockLayer> layers,
+        IRepository<StockLedger> ledger, IRepository<StockTransferLine> transferLines)
+    {
+        _fifo = fifo;
+        _layers = layers;
+        _ledger = ledger;
+        _transferLines = transferLines;
+    }
+
+    public async Task<StockOnHandDto> GetOnHandAsync(long itemId, long warehouseId, CancellationToken ct = default)
+    {
+        var onHand = await _fifo.GetOnHandAsync(itemId, warehouseId, ct);
+
+        // On-hold stock is on-hand but not issuable — sourced from GRN lines still OnHold.
+        var onHold = await _layers.Query().AsNoTracking()
+            .Where(l => l.ItemId == itemId && l.WarehouseId == warehouseId
+                        && l.GrnLine != null && l.GrnLine.HoldStatus == HoldStatus.OnHold)
+            .SumAsync(l => (decimal?)l.QtyRemaining, ct) ?? 0m;
+
+        // Outbound in-transit: dispatched from this warehouse, not yet received at the
+        // destination. Dispatch already consumed the source layers, so this stock has
+        // left onHand — it is reported for visibility (AR-05) but is NOT re-subtracted
+        // from available (that would double-count). reserved (sales) stays a stub.
+        var inTransit = await _transferLines.Query().AsNoTracking()
+            .Where(l => l.ItemId == itemId
+                        && l.Transfer!.SrcWarehouseId == warehouseId
+                        && l.Transfer.Status == TransferStatus.InTransit)
+            .SumAsync(l => (decimal?)(l.Qty - l.QtyReceived), ct) ?? 0m;
+        const decimal reserved = 0m;
+        var available = onHand - onHold - reserved;
+
+        return new StockOnHandDto(itemId, warehouseId, onHand, available, onHold, inTransit, reserved, DateTime.UtcNow);
+    }
+
+    public async Task<PagedResponse<StockLedgerRowDto>> GetLedgerAsync(
+        long? itemId, long? warehouseId, DateOnly? from, DateOnly? to, PageQuery query, CancellationToken ct = default)
+    {
+        var q = _ledger.Query().AsNoTracking();
+        if (itemId is not null) q = q.Where(l => l.ItemId == itemId);
+        if (warehouseId is not null) q = q.Where(l => l.WarehouseId == warehouseId);
+        if (from is not null) q = q.Where(l => l.CreatedAt >= from.Value.ToDateTime(TimeOnly.MinValue));
+        if (to is not null) q = q.Where(l => l.CreatedAt < to.Value.AddDays(1).ToDateTime(TimeOnly.MinValue));
+
+        var total = await q.CountAsync(ct);
+        var rows = await q.OrderByDescending(l => l.LedgerId)
+            .Skip(query.Skip).Take(query.PageSize)
+            .Select(l => new StockLedgerRowDto(
+                l.LedgerId, l.ItemId, l.WarehouseId, l.BinId, l.BatchId, l.SerialId,
+                l.Direction, l.QtyBase, l.UnitCost, l.Value, l.RunningBalance,
+                l.SourceDocType, l.SourceDocId, l.UserId, l.CreatedAt))
+            .ToListAsync(ct);
+
+        return PagedResponse<StockLedgerRowDto>.Create(rows, query.Page, query.PageSize, total);
+    }
+
+    public Task<StockValuationDto> GetValuationAsync(long itemId, long warehouseId, CancellationToken ct = default)
+        => _fifo.GetValuationAsync(itemId, warehouseId, ct);
+}

Backend/ERPCore/Services/TransferService.cs

@@ -0,0 +1,196 @@
+using ERPCore.Domain;
+using ERPCore.Domain.Entities;
+using ERPCore.Domain.Enums;
+using ERPCore.Dtos.Stock;
+using ERPCore.Infra.Auth;
+using ERPCore.Infra.UoW;
+using ERPCore.Repositories.Interfaces;
+using ERPCore.Services.Interfaces;
+using ERPCore.System.Errors;
+using Microsoft.EntityFrameworkCore;
+
+namespace ERPCore.Services;
+
+/// <summary>
+/// Inter-warehouse transfer service (FR-STK-05/06). Dispatch consumes source FIFO
+/// layers (row-locked; negative-stock blocked) and records the value-weighted cost
+/// on the line; receive recreates the destination layer at that cost
+/// (cost-preserving — no revaluation). Both run in a single UoW transaction.
+/// </summary>
+public sealed class TransferService : ITransferService
+{
+    private readonly IRepository<StockTransfer> _transfers;
+    private readonly IRepository<Warehouse> _warehouses;
+    private readonly IRepository<Item> _items;
+    private readonly IFifoCostingService _fifo;
+    private readonly INumberSequenceService _numbers;
+    private readonly ICurrentUser _currentUser;
+    private readonly IUnitOfWork _uow;
+
+    public TransferService(
+        IRepository<StockTransfer> transfers, IRepository<Warehouse> warehouses, IRepository<Item> items,
+        IFifoCostingService fifo, INumberSequenceService numbers, ICurrentUser currentUser, IUnitOfWork uow)
+    {
+        _transfers = transfers;
+        _warehouses = warehouses;
+        _items = items;
+        _fifo = fifo;
+        _numbers = numbers;
+        _currentUser = currentUser;
+        _uow = uow;
+    }
+
+    public async Task<TransferDto?> GetAsync(long transferId, CancellationToken ct = default)
+    {
+        var t = await _transfers.Query().AsNoTracking().Include(x => x.Lines)
+            .FirstOrDefaultAsync(x => x.TransferId == transferId, ct);
+        return t is null ? null : Map(t);
+    }
+
+    public async Task<TransferDto> CreateAsync(CreateTransferRequest request, CancellationToken ct = default)
+    {
+        if (request.SrcWarehouseId == request.DestWarehouseId)
+            throw new DomainException(ErrorCodes.Validation, "destWarehouseId must differ from srcWarehouseId.", 422);
+        await EnsureWarehouseAsync(request.SrcWarehouseId, ct);
+        await EnsureWarehouseAsync(request.DestWarehouseId, ct);
+        foreach (var line in request.Lines)
+            if (!await _items.Query().AnyAsync(i => i.ItemId == line.ItemId, ct))
+                throw new DomainException(ErrorCodes.Validation, $"Item {line.ItemId} does not exist.", 422);
+
+        var actor = _currentUser.AuditUserId;
+        var transfer = await _uow.ExecuteInTransactionAsync(async token =>
+        {
+            var docNo = await _numbers.NextAsync(DocumentTypes.Transfer, token);
+            var entity = new StockTransfer
+            {
+                DocNo = docNo,
+                SrcWarehouseId = request.SrcWarehouseId,
+                DestWarehouseId = request.DestWarehouseId,
+                Status = TransferStatus.Draft,
+                CreatedBy = actor,
+                CreatedAt = DateTime.UtcNow,
+                Lines = request.Lines.Select(l => new StockTransferLine
+                {
+                    ItemId = l.ItemId,
+                    SrcBinId = l.SrcBinId,
+                    DestBinId = l.DestBinId,
+                    BatchId = l.BatchId,
+                    Qty = l.Qty
+                }).ToList()
+            };
+            await _transfers.AddAsync(entity, token);
+            return entity;
+        }, ct);
+
+        return Map(transfer);
+    }
+
+    public async Task<DispatchResultDto> DispatchAsync(long transferId, CancellationToken ct = default)
+    {
+        var transfer = await _transfers.Query().Include(t => t.Lines)
+            .FirstOrDefaultAsync(t => t.TransferId == transferId, ct)
+            ?? throw new NotFoundException($"Transfer {transferId} was not found.");
+        if (transfer.Status != TransferStatus.Draft)
+            throw new ConflictException($"Transfer {transferId} is {transfer.Status}; only a Draft can be dispatched.");
+
+        var actor = _currentUser.AuditUserId;
+        var now = DateTime.UtcNow;
+        var consumed = new List<ConsumedLayerDto>();
+        var ledgerRefs = new List<StockLedger>();
+        var balances = new Dictionary<long, decimal>();
+
+        await _uow.ExecuteInTransactionAsync(async token =>
+        {
+            foreach (var line in transfer.Lines.OrderBy(l => l.TransferLineId))
+            {
+                var segments = await _fifo.ConsumeAsync(line.ItemId, transfer.SrcWarehouseId, line.BatchId, line.Qty, token);
+                var value = segments.Sum(s => s.Qty * s.UnitCost);
+                line.UnitCost = value / line.Qty; // value-weighted cost, preserved to receive
+
+                if (!balances.TryGetValue(line.ItemId, out var bal))
+                    bal = await _fifo.GetOnHandAsync(line.ItemId, transfer.SrcWarehouseId, token);
+                bal -= line.Qty;
+                balances[line.ItemId] = bal;
+
+                var entry = await _fifo.PostLedgerAsync(
+                    line.ItemId, transfer.SrcWarehouseId, line.SrcBinId, line.BatchId, null, actor,
+                    Direction.Out, line.Qty, line.UnitCost.Value, bal, DocumentTypes.Transfer, transfer.TransferId, now, token);
+                ledgerRefs.Add(entry);
+
+                consumed.AddRange(segments.Select(s => new ConsumedLayerDto(s.LayerId, s.Qty, s.UnitCost)));
+            }
+
+            transfer.Status = TransferStatus.InTransit;
+            return 0;
+        }, ct);
+
+        return new DispatchResultDto(transfer.TransferId, transfer.Status, consumed, ledgerRefs.Select(l => l.LedgerId).ToList());
+    }
+
+    public async Task<ReceiveResultDto> ReceiveAsync(long transferId, ReceiveTransferRequest request, CancellationToken ct = default)
+    {
+        var transfer = await _transfers.Query().Include(t => t.Lines)
+            .FirstOrDefaultAsync(t => t.TransferId == transferId, ct)
+            ?? throw new NotFoundException($"Transfer {transferId} was not found.");
+        if (transfer.Status != TransferStatus.InTransit)
+            throw new ConflictException($"Transfer {transferId} is {transfer.Status}; only an InTransit transfer can be received.");
+
+        var actor = _currentUser.AuditUserId;
+        var now = DateTime.UtcNow;
+        var createdLayers = new List<StockLayer>();
+        var ledgerRefs = new List<StockLedger>();
+        var balances = new Dictionary<long, decimal>();
+
+        await _uow.ExecuteInTransactionAsync(async token =>
+        {
+            foreach (var input in request.Lines)
+            {
+                var line = transfer.Lines.FirstOrDefault(l => l.TransferLineId == input.TransferLineId)
+                    ?? throw new DomainException(ErrorCodes.Validation, $"Transfer line {input.TransferLineId} is not on transfer {transferId}.", 422);
+
+                var outstanding = line.Qty - line.QtyReceived;
+                if (input.Qty > outstanding)
+                    throw new DomainException(ErrorCodes.Validation,
+                        $"Receiving {input.Qty} exceeds the outstanding in-transit {outstanding} on line {input.TransferLineId}.", 422);
+
+                var unitCost = line.UnitCost ?? 0m;
+                var layer = await _fifo.CreateInboundLayerAsync(
+                    line.ItemId, transfer.DestWarehouseId, line.BatchId, null, null, input.Qty, unitCost, now, token);
+                createdLayers.Add(layer);
+
+                if (!balances.TryGetValue(line.ItemId, out var bal))
+                    bal = await _fifo.GetOnHandAsync(line.ItemId, transfer.DestWarehouseId, token);
+                bal += input.Qty;
+                balances[line.ItemId] = bal;
+
+                var entry = await _fifo.PostLedgerAsync(
+                    line.ItemId, transfer.DestWarehouseId, line.DestBinId, line.BatchId, null, actor,
+                    Direction.In, input.Qty, unitCost, bal, DocumentTypes.Transfer, transfer.TransferId, now, token);
+                ledgerRefs.Add(entry);
+
+                line.QtyReceived += input.Qty;
+            }
+
+            if (transfer.Lines.All(l => l.QtyReceived >= l.Qty))
+                transfer.Status = TransferStatus.Received;
+            return 0;
+        }, ct);
+
+        // Map after commit so layer ids are populated.
+        var created = createdLayers
+            .Select(l => new TransferCreatedLayerDto(l.LayerId, l.WarehouseId, l.QtyReceived, l.UnitCost))
+            .ToList();
+        return new ReceiveResultDto(transfer.TransferId, transfer.Status, created, ledgerRefs.Select(l => l.LedgerId).ToList());
+    }
+
+    private async Task EnsureWarehouseAsync(long warehouseId, CancellationToken ct)
+    {
+        if (!await _warehouses.Query().AnyAsync(w => w.WarehouseId == warehouseId, ct))
+            throw new DomainException(ErrorCodes.Validation, $"Warehouse {warehouseId} does not exist.", 422);
+    }
+
+    private static TransferDto Map(StockTransfer t) => new(
+        t.TransferId, t.DocNo, t.SrcWarehouseId, t.DestWarehouseId, t.Status,
+        t.Lines.OrderBy(l => l.TransferLineId).Select(l => new TransferLineDto(
+            l.TransferLineId, l.ItemId, l.SrcBinId, l.DestBinId, l.BatchId, l.Qty, l.QtyReceived)).ToList());
+}