feat: add purchase invoice batch print page and related components

- Implemented PurchaseInvoiceBatchPrintPage for printing purchase invoices.
- Created InvoicePrintHeader and InvoicePrintFooter components for invoice layout.
- Added invoice layout presets for different styles (Classic, Compact, Modern).
- Developed PurchaseInvoicePaymentDialog for handling payments against invoices.
- Introduced API mocks for company profile and invoice template configuration.
- Added validation functions for company profile and purchase invoices.
- Defined types for company profile, invoice template configuration, and purchase invoices.

Backend/ERPCore/Controllers/GrnsController.cs

@@ -11,12 +11,10 @@ namespace ERPCore.Controllers;
 public sealed class GrnsController : ApiControllerBase
 {
     private readonly IGrnService _grns;
-    private readonly IGrnPaymentService _payments;
 
-    public GrnsController(IGrnService grns, IGrnPaymentService payments)
+    public GrnsController(IGrnService grns)
     {
         _grns = grns;
-        _payments = payments;
     }
 
     /// <summary>List GRNs, newest first.</summary>
@@ -64,23 +62,4 @@ public sealed class GrnsController : ApiControllerBase
     public async Task<ActionResult<ReleaseLineResultDto>> Release(
         int grnId, int grnLineId, [FromBody] ReleaseLineRequest request, CancellationToken ct)
         => Ok(await _grns.ReleaseLineAsync(grnId, grnLineId, request.Action, ct));
-
-    /// <summary>Pay the vendor against this GRN's balance, in full or in installments; posts a real GL journal entry.</summary>
-    [HttpPost("{grnId:int}/payments")]
-    [ProducesResponseType(typeof(GrnPaymentDto), StatusCodes.Status201Created)]
-    [ProducesResponseType(StatusCodes.Status400BadRequest)]
-    [ProducesResponseType(StatusCodes.Status404NotFound)]
-    [ProducesResponseType(StatusCodes.Status409Conflict)]
-    public async Task<ActionResult<GrnPaymentDto>> Pay(int grnId, [FromBody] CreateGrnPaymentRequest request, CancellationToken ct)
-    {
-        var dto = await _payments.PayAsync(grnId, request, ct);
-        return Created($"/api/v1/grns/{grnId}/payments/{dto.GrnPaymentId}", dto);
-    }
-
-    /// <summary>Payment history for this GRN, newest first.</summary>
-    [HttpGet("{grnId:int}/payments")]
-    [ProducesResponseType(typeof(IReadOnlyList<GrnPaymentDto>), StatusCodes.Status200OK)]
-    [ProducesResponseType(StatusCodes.Status404NotFound)]
-    public async Task<ActionResult<IReadOnlyList<GrnPaymentDto>>> ListPayments(int grnId, CancellationToken ct)
-        => Ok(await _payments.ListAsync(grnId, ct));
 }

Backend/ERPCore/Controllers/PurchaseInvoicesController.cs

@@ -0,0 +1,102 @@
+using ERPCore.Domain.Enums;
+using ERPCore.Dtos.Common;
+using ERPCore.Dtos.Grn;
+using ERPCore.Dtos.Procurement;
+using ERPCore.Services.Interfaces;
+using Microsoft.AspNetCore.Mvc;
+
+namespace ERPCore.Controllers;
+
+/// <summary>Purchase invoice endpoints — vendor invoices consolidating Confirmed GRNs.</summary>
+[Route("api/v1/purchase-invoices")]
+public sealed class PurchaseInvoicesController : ApiControllerBase
+{
+    private readonly IPurchaseInvoiceService _invoices;
+    private readonly IPurchaseInvoicePaymentService _payments;
+
+    public PurchaseInvoicesController(IPurchaseInvoiceService invoices, IPurchaseInvoicePaymentService payments)
+    {
+        _invoices = invoices;
+        _payments = payments;
+    }
+
+    [HttpGet]
+    [ProducesResponseType(typeof(PagedResponse<PurchaseInvoiceSummaryDto>), StatusCodes.Status200OK)]
+    public async Task<ActionResult<PagedResponse<PurchaseInvoiceSummaryDto>>> List(
+        [FromQuery] PageQuery query, [FromQuery] PurchaseInvoiceStatus? status, [FromQuery] int? vendorId, CancellationToken ct)
+        => Ok(await _invoices.ListAsync(query, status, vendorId, ct));
+
+    /// <summary>Confirmed, not-yet-invoiced GRNs for a vendor — candidates for a new/edited invoice.</summary>
+    [HttpGet("eligible-grns")]
+    [ProducesResponseType(typeof(IReadOnlyList<GrnEligibleForInvoiceDto>), StatusCodes.Status200OK)]
+    public async Task<ActionResult<IReadOnlyList<GrnEligibleForInvoiceDto>>> EligibleGrns([FromQuery] int vendorId, CancellationToken ct)
+        => Ok(await _invoices.ListEligibleGrnsAsync(vendorId, ct));
+
+    [HttpGet("{purchaseInvoiceId:int}")]
+    [ProducesResponseType(typeof(PurchaseInvoiceDto), StatusCodes.Status200OK)]
+    [ProducesResponseType(StatusCodes.Status404NotFound)]
+    public async Task<ActionResult<PurchaseInvoiceDto>> GetById(int purchaseInvoiceId, CancellationToken ct)
+    {
+        var result = await _invoices.GetAsync(purchaseInvoiceId, ct);
+        if (result is null) return NotFound();
+        SetETag(result.RowVersion);
+        return Ok(result.Value);
+    }
+
+    [HttpPost]
+    [ProducesResponseType(typeof(PurchaseInvoiceDto), StatusCodes.Status201Created)]
+    [ProducesResponseType(StatusCodes.Status409Conflict)]
+    [ProducesResponseType(StatusCodes.Status422UnprocessableEntity)]
+    public async Task<ActionResult<PurchaseInvoiceDto>> Create([FromBody] CreatePurchaseInvoiceRequest request, CancellationToken ct)
+    {
+        var result = await _invoices.CreateAsync(request, ct);
+        SetETag(result.RowVersion);
+        return Created($"/api/v1/purchase-invoices/{result.Value.PurchaseInvoiceId}", result.Value);
+    }
+
+    [HttpPut("{purchaseInvoiceId:int}")]
+    [ProducesResponseType(typeof(PurchaseInvoiceDto), StatusCodes.Status200OK)]
+    [ProducesResponseType(StatusCodes.Status404NotFound)]
+    [ProducesResponseType(StatusCodes.Status409Conflict)]
+    [ProducesResponseType(StatusCodes.Status412PreconditionFailed)]
+    public async Task<ActionResult<PurchaseInvoiceDto>> Update(int purchaseInvoiceId, [FromBody] UpdatePurchaseInvoiceRequest request, CancellationToken ct)
+    {
+        var expected = RequireIfMatch();
+        var result = await _invoices.UpdateAsync(purchaseInvoiceId, request, expected, ct);
+        SetETag(result.RowVersion);
+        return Ok(result.Value);
+    }
+
+    [HttpPost("{purchaseInvoiceId:int}/post")]
+    [ProducesResponseType(typeof(PurchaseInvoiceDto), StatusCodes.Status200OK)]
+    [ProducesResponseType(StatusCodes.Status404NotFound)]
+    [ProducesResponseType(StatusCodes.Status409Conflict)]
+    public async Task<ActionResult<PurchaseInvoiceDto>> Post(int purchaseInvoiceId, CancellationToken ct)
+        => Ok(await _invoices.PostAsync(purchaseInvoiceId, ct));
+
+    [HttpPost("{purchaseInvoiceId:int}/cancel")]
+    [ProducesResponseType(typeof(PurchaseInvoiceDto), StatusCodes.Status200OK)]
+    [ProducesResponseType(StatusCodes.Status404NotFound)]
+    [ProducesResponseType(StatusCodes.Status409Conflict)]
+    public async Task<ActionResult<PurchaseInvoiceDto>> Cancel(int purchaseInvoiceId, CancellationToken ct)
+        => Ok(await _invoices.CancelAsync(purchaseInvoiceId, ct));
+
+    /// <summary>Pay the vendor against this invoice's balance, in full or in installments; posts a real GL journal entry.</summary>
+    [HttpPost("{purchaseInvoiceId:int}/payments")]
+    [ProducesResponseType(typeof(PurchaseInvoicePaymentDto), StatusCodes.Status201Created)]
+    [ProducesResponseType(StatusCodes.Status400BadRequest)]
+    [ProducesResponseType(StatusCodes.Status404NotFound)]
+    [ProducesResponseType(StatusCodes.Status409Conflict)]
+    public async Task<ActionResult<PurchaseInvoicePaymentDto>> Pay(int purchaseInvoiceId, [FromBody] CreatePurchaseInvoicePaymentRequest request, CancellationToken ct)
+    {
+        var dto = await _payments.PayAsync(purchaseInvoiceId, request, ct);
+        return Created($"/api/v1/purchase-invoices/{purchaseInvoiceId}/payments/{dto.PurchaseInvoicePaymentId}", dto);
+    }
+
+    /// <summary>Payment history for this invoice, newest first.</summary>
+    [HttpGet("{purchaseInvoiceId:int}/payments")]
+    [ProducesResponseType(typeof(IReadOnlyList<PurchaseInvoicePaymentDto>), StatusCodes.Status200OK)]
+    [ProducesResponseType(StatusCodes.Status404NotFound)]
+    public async Task<ActionResult<IReadOnlyList<PurchaseInvoicePaymentDto>>> ListPayments(int purchaseInvoiceId, CancellationToken ct)
+        => Ok(await _payments.ListAsync(purchaseInvoiceId, ct));
+}

Backend/ERPCore/Domain/DocumentTypes.cs

@@ -10,6 +10,7 @@ public static class DocumentTypes
     public const string Rfq = "RFQ";
     public const string PurchaseOrder = "PO";
     public const string Grn = "GRN";
+    public const string PurchaseInvoice = "PINV";
     public const string Transfer = "TRF";
     public const string Adjustment = "ADJ";
     public const string Count = "CNT";

Backend/ERPCore/Domain/Entities/Grn.cs

@@ -34,14 +34,14 @@ public class Grn
     public string? GlJournalNo { get; set; }
     public DateTime? GlPostedAt { get; set; }
 
-    /// <summary>Sum of vendor payments made against this GRN's total payable (<see cref="GrnLine.LineTotal"/>).</summary>
-    public decimal PaidAmount { get; set; }
-    /// <summary>Total payable minus <see cref="PaidAmount"/>; installments accrue against this until it reaches zero.</summary>
-    public decimal BalanceAmount { get; set; }
+    /// <summary>The Purchase Invoice this GRN has been consolidated into, if any (null until
+    /// invoiced). Vendor settlement is tracked on the invoice, not per-GRN — see
+    /// <see cref="PurchaseInvoice"/>.</summary>
+    public int? PurchaseInvoiceId { get; set; }
+    public PurchaseInvoice? PurchaseInvoice { get; set; }
 
     /// <summary>PostgreSQL xmin-backed optimistic concurrency token.</summary>
     public uint RowVersion { get; set; }
 
     public ICollection<GrnLine> Lines { get; set; } = new List<GrnLine>();
-    public ICollection<GrnPayment> Payments { get; set; } = new List<GrnPayment>();
 }

Backend/ERPCore/Domain/Entities/PurchaseInvoice.cs

@@ -0,0 +1,50 @@
+using ERPCore.Domain.Enums;
+
+namespace ERPCore.Domain.Entities;
+
+/// <summary>
+/// Vendor invoice consolidating one or more Confirmed GRNs for the same vendor
+/// (each linked GRN becomes one <see cref="PurchaseInvoiceLine"/>, not re-itemized).
+/// Draft is editable (GRNs can be re-selected); Posted reclassifies the GRN clearing
+/// balance to Accounts Payable (see PurchaseInvoiceService.PostAsync); vendor payments
+/// are then recorded against this aggregate rather than against the individual GRNs.
+/// </summary>
+public class PurchaseInvoice
+{
+    public int PurchaseInvoiceId { get; set; }
+    public string DocNo { get; set; } = string.Empty;
+
+    public string VendorInvoiceNo { get; set; } = string.Empty;
+    public DateTime VendorInvoiceDate { get; set; }
+
+    public int VendorId { get; set; }
+    public Vendor? Vendor { get; set; }
+
+    public string VendorSnapshotName { get; set; } = string.Empty;
+    public string? VendorSnapshotTaxNo { get; set; }
+
+    public PurchaseInvoiceStatus Status { get; set; } = PurchaseInvoiceStatus.Draft;
+
+    public decimal Subtotal { get; set; }
+    public decimal VatTotal { get; set; }
+    public decimal GrandTotal { get; set; }
+    public decimal PaidAmount { get; set; }
+    public decimal BalanceAmount { get; set; }
+
+    /// <summary>Journal number of the AP-recognition GL journal entry posted when this
+    /// invoice is Posted (Debit GRN Clearing / Credit Accounts Payable) — see
+    /// PurchaseInvoiceService.PostAsync.</summary>
+    public string? GlJournalNo { get; set; }
+    public DateTime? GlPostedAt { get; set; }
+
+    public int CreatedBy { get; set; }
+    public User? Creator { get; set; }
+
+    public DateTime CreatedAt { get; set; }
+    public DateTime? UpdatedAt { get; set; }
+
+    public uint RowVersion { get; set; }
+
+    public ICollection<PurchaseInvoiceLine> Lines { get; set; } = new List<PurchaseInvoiceLine>();
+    public ICollection<PurchaseInvoicePayment> Payments { get; set; } = new List<PurchaseInvoicePayment>();
+}

Backend/ERPCore/Domain/Entities/PurchaseInvoiceLine.cs

@@ -0,0 +1,21 @@
+namespace ERPCore.Domain.Entities;
+
+/// <summary>
+/// One row per consolidated GRN on a <see cref="PurchaseInvoice"/> — a straight
+/// consolidation of that GRN's line totals, not a re-itemization (docs: Purchase
+/// Invoice consolidates GRNs, it does not re-enter item lines).
+/// </summary>
+public class PurchaseInvoiceLine
+{
+    public int PurchaseInvoiceLineId { get; set; }
+
+    public int PurchaseInvoiceId { get; set; }
+    public PurchaseInvoice? PurchaseInvoice { get; set; }
+
+    public int GrnId { get; set; }
+    public Grn? Grn { get; set; }
+
+    public decimal Subtotal { get; set; }
+    public decimal VatTotal { get; set; }
+    public decimal LineTotal { get; set; }
+}

Backend/ERPCore/Domain/Entities/PurchaseInvoicePayment.cs

@@ -1,16 +1,17 @@
 namespace ERPCore.Domain.Entities;
 
 /// <summary>
-/// A vendor payment made against a confirmed GRN's balance (installments allowed —
-/// see GrnPaymentService.PayAsync). Posts its own real GL journal entry (Debit GRN
-/// Clearing / Credit the selected bank-or-cash account) before being recorded here.
+/// A vendor payment made against a Posted purchase invoice's balance (installments
+/// allowed — see PurchaseInvoicePaymentService.PayAsync). Posts its own real GL
+/// journal entry (Debit Accounts Payable / Credit the selected bank-or-cash account)
+/// before being recorded here.
 /// </summary>
-public class GrnPayment
+public class PurchaseInvoicePayment
 {
-    public int GrnPaymentId { get; set; }
+    public int PurchaseInvoicePaymentId { get; set; }
 
-    public int GrnId { get; set; }
-    public Grn? Grn { get; set; }
+    public int PurchaseInvoiceId { get; set; }
+    public PurchaseInvoice? PurchaseInvoice { get; set; }
 
     public decimal Amount { get; set; }
     public DateTime PaymentDate { get; set; }

Backend/ERPCore/Domain/Entities/SalesInvoicePayment.cs

@@ -4,7 +4,7 @@ namespace ERPCore.Domain.Entities;
 /// A customer payment made against a Posted sales invoice's balance (installments
 /// allowed — see SalesInvoicePaymentService.PayAsync). Posts its own real GL journal
 /// entry (Debit the selected bank-or-cash account / Credit Accounts Receivable) before
-/// being recorded here — the mirror image of <see cref="GrnPayment"/>.
+/// being recorded here — the mirror image of <see cref="PurchaseInvoicePayment"/>.
 /// </summary>
 public class SalesInvoicePayment
 {

Backend/ERPCore/Domain/Enums/PurchaseInvoiceStatus.cs

@@ -0,0 +1,8 @@
+namespace ERPCore.Domain.Enums;
+
+public enum PurchaseInvoiceStatus
+{
+    Draft,
+    Posted,
+    Cancelled
+}

Backend/ERPCore/Dtos/Grn/GrnDtos.cs

@@ -17,34 +17,28 @@ public sealed record GrnLineDto(
 public sealed record GrnDto(
     int GrnId, string DocNo, int? PoId, int VendorId, int WarehouseId, GrnStatus Status,
     int CreatedBy, DateTime CreatedAt, DateTime? PostedAt, string? GlJournalNo,
-    decimal PaidAmount, decimal BalanceAmount, IReadOnlyList<GrnLineDto> Lines);
+    int? PurchaseInvoiceId, string? PurchaseInvoiceNo, IReadOnlyList<GrnLineDto> Lines);
 
 /// <summary>Row shape for <c>GET /grns</c> — line count instead of the lines themselves.</summary>
 public sealed record GrnSummaryDto(
     int GrnId, string DocNo, int? PoId, int VendorId, int WarehouseId, GrnStatus Status,
     int CreatedBy, DateTime CreatedAt, DateTime? PostedAt, int LineCount,
-    decimal PaidAmount, decimal BalanceAmount);
+    int? PurchaseInvoiceId, string? PurchaseInvoiceNo);
 
 public sealed record CreatedLayerDto(
     int LayerId, int ItemId, int WarehouseId, int? BatchId,
     decimal QtyReceived, decimal QtyRemaining, decimal UnitCost, DateTime ReceiptDate);
 
 public sealed record GrnConfirmResultDto(
-    int GrnId, GrnStatus Status, DateTime PostedAt, string GlJournalNo, decimal BalanceAmount,
+    int GrnId, GrnStatus Status, DateTime PostedAt, string GlJournalNo,
     IReadOnlyList<CreatedLayerDto> CreatedLayers, IReadOnlyList<int> LedgerRefs, PurchaseOrderStatus? PoStatus);
 
 public sealed record ReleaseLineResultDto(int GrnLineId, HoldStatus HoldStatus);
 
-public sealed record GrnPaymentDto(
-    int GrnPaymentId, int GrnId, decimal Amount, DateTime PaymentDate,
-    long GlBankAccountId, string BankAccountName, string? Reference, string? GlJournalNo, DateTime CreatedAt);
-
-public sealed class CreateGrnPaymentRequest
-{
-    [Range(0.01, double.MaxValue)] public decimal Amount { get; set; }
-    [Required] public long GlBankAccountId { get; set; }
-    [StringLength(100)] public string? Reference { get; set; }
-}
+/// <summary>A Confirmed, not-yet-invoiced GRN eligible to be consolidated onto a Purchase Invoice.</summary>
+public sealed record GrnEligibleForInvoiceDto(
+    int GrnId, string DocNo, DateTime PostedAt, int WarehouseId,
+    int LineCount, decimal Subtotal, decimal VatTotal, decimal GrandTotal);
 
 // Requests ----------------------------------------------------------------------
 

Backend/ERPCore/Dtos/Procurement/PurchaseInvoiceDtos.cs

@@ -0,0 +1,50 @@
+using System.ComponentModel.DataAnnotations;
+using ERPCore.Domain.Enums;
+
+namespace ERPCore.Dtos.Procurement;
+
+public sealed record PurchaseInvoiceLineDto(
+    int PurchaseInvoiceLineId, int GrnId, string GrnDocNo, DateTime GrnPostedAt,
+    decimal Subtotal, decimal VatTotal, decimal LineTotal);
+
+public sealed record PurchaseInvoiceTotalsDto(
+    decimal Subtotal, decimal VatTotal, decimal GrandTotal, decimal PaidAmount, decimal BalanceAmount);
+
+public sealed record PurchaseInvoiceDto(
+    int PurchaseInvoiceId, string DocNo, string VendorInvoiceNo, DateTime VendorInvoiceDate,
+    int VendorId, string VendorSnapshotName, string? VendorSnapshotTaxNo,
+    PurchaseInvoiceStatus Status, int GrnCount, int CreatedBy, DateTime CreatedAt, DateTime? UpdatedAt,
+    string? GlJournalNo, DateTime? GlPostedAt,
+    PurchaseInvoiceTotalsDto Totals, IReadOnlyList<PurchaseInvoiceLineDto> Lines);
+
+public sealed record PurchaseInvoiceSummaryDto(
+    int PurchaseInvoiceId, string DocNo, string VendorInvoiceNo, DateTime VendorInvoiceDate,
+    int VendorId, string VendorSnapshotName, PurchaseInvoiceStatus Status, int GrnCount,
+    PurchaseInvoiceTotalsDto Totals, DateTime CreatedAt, string? GlJournalNo);
+
+public sealed record PurchaseInvoicePaymentDto(
+    int PurchaseInvoicePaymentId, int PurchaseInvoiceId, decimal Amount, DateTime PaymentDate,
+    long GlBankAccountId, string BankAccountName, string? Reference, string? GlJournalNo, DateTime CreatedAt);
+
+public sealed class CreatePurchaseInvoicePaymentRequest
+{
+    [Range(0.01, double.MaxValue)] public decimal Amount { get; set; }
+    [Required] public long GlBankAccountId { get; set; }
+    [StringLength(100)] public string? Reference { get; set; }
+}
+
+public sealed class CreatePurchaseInvoiceRequest
+{
+    [Required] public int VendorId { get; set; }
+    [Required, StringLength(50)] public string VendorInvoiceNo { get; set; } = string.Empty;
+    [Required] public DateTime VendorInvoiceDate { get; set; }
+    [Required, MinLength(1)] public List<int> GrnIds { get; set; } = new();
+}
+
+public sealed class UpdatePurchaseInvoiceRequest
+{
+    [Required] public int VendorId { get; set; }
+    [Required, StringLength(50)] public string VendorInvoiceNo { get; set; } = string.Empty;
+    [Required] public DateTime VendorInvoiceDate { get; set; }
+    [Required, MinLength(1)] public List<int> GrnIds { get; set; } = new();
+}

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

@@ -17,41 +17,19 @@ public sealed class GrnConfiguration : IEntityTypeConfiguration<Grn>
         builder.Property(g => g.Status).HasConversion<string>().HasMaxLength(20).IsRequired();
         builder.Property(g => g.CreatedAt).IsRequired();
         builder.Property(g => g.GlJournalNo).HasMaxLength(30);
-        builder.Property(g => g.PaidAmount).HasPrecision(18, 4);
-        builder.Property(g => g.BalanceAmount).HasPrecision(18, 4);
         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.HasOne(g => g.PurchaseInvoice).WithMany().HasForeignKey(g => g.PurchaseInvoiceId).OnDelete(DeleteBehavior.Restrict);
 
         builder.HasIndex(g => g.Status);
         builder.HasIndex(g => g.PoId);
     }
 }
 
-public sealed class GrnPaymentConfiguration : IEntityTypeConfiguration<GrnPayment>
-{
-    public void Configure(EntityTypeBuilder<GrnPayment> builder)
-    {
-        builder.ToTable("grn_payments");
-        builder.HasKey(p => p.GrnPaymentId);
-
-        builder.Property(p => p.Amount).HasPrecision(18, 4);
-        builder.Property(p => p.PaymentDate).IsRequired();
-        builder.Property(p => p.BankAccountName).IsRequired().HasMaxLength(200);
-        builder.Property(p => p.Reference).HasMaxLength(100);
-        builder.Property(p => p.GlJournalNo).HasMaxLength(30);
-        builder.Property(p => p.CreatedAt).IsRequired();
-
-        builder.HasOne(p => p.Grn).WithMany(g => g.Payments).HasForeignKey(p => p.GrnId).OnDelete(DeleteBehavior.Restrict);
-        builder.HasOne(p => p.Creator).WithMany().HasForeignKey(p => p.CreatedBy).OnDelete(DeleteBehavior.Restrict);
-
-        builder.HasIndex(p => p.GrnId);
-    }
-}
-
 public sealed class GrnLineConfiguration : IEntityTypeConfiguration<GrnLine>
 {
     public void Configure(EntityTypeBuilder<GrnLine> builder)

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

@@ -63,9 +63,10 @@ public sealed class PermissionConfiguration : IEntityTypeConfiguration<Permissio
             new Permission { PermissionId = 33, Code = "NAV:accounts.cheque-books", SubNavItemId = 21 },
             new Permission { PermissionId = 34, Code = "NAV:accounts.received-cheques", SubNavItemId = 22 },
             new Permission { PermissionId = 35, Code = "NAV:production", NavItemId = 14 },
-            new Permission { PermissionId = 36, Code = "NAV:production.templates", SubNavItemId = 24 },
+            new Permission { PermissionId = 36, Code = "NAV:production.templates", SubNavItemId = 27 },
             new Permission { PermissionId = 37, Code = "NAV:production.runs", SubNavItemId = 25 },
-            new Permission { PermissionId = 38, Code = "NAV:production.produced", SubNavItemId = 26 }
+            new Permission { PermissionId = 38, Code = "NAV:production.produced", SubNavItemId = 26 },
+            new Permission { PermissionId = 39, Code = "NAV:procurement.purchase-invoices", SubNavItemId = 28 }
         );
     }
 }

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

@@ -0,0 +1,97 @@
+using ERPCore.Domain.Entities;
+using ERPCore.Domain.Enums;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Metadata.Builders;
+
+namespace ERPCore.Infra.Persistence.Configurations;
+
+public sealed class PurchaseInvoiceConfiguration : IEntityTypeConfiguration<PurchaseInvoice>
+{
+    public void Configure(EntityTypeBuilder<PurchaseInvoice> builder)
+    {
+        builder.ToTable("purchase_invoices");
+        builder.HasKey(x => x.PurchaseInvoiceId);
+
+        builder.Property(x => x.DocNo).IsRequired().HasMaxLength(30);
+        builder.HasIndex(x => x.DocNo).IsUnique();
+
+        builder.Property(x => x.VendorInvoiceNo).IsRequired().HasMaxLength(50);
+        builder.Property(x => x.VendorInvoiceDate).IsRequired();
+        // A vendor invoice number is only meaningful per-vendor; the service also excludes
+        // Cancelled invoices from the duplicate check, so this composite index is a coarse
+        // backstop (it does not distinguish Cancelled rows) rather than the sole enforcement.
+        builder.HasIndex(x => new { x.VendorId, x.VendorInvoiceNo });
+
+        builder.HasOne(x => x.Vendor)
+            .WithMany()
+            .HasForeignKey(x => x.VendorId)
+            .OnDelete(DeleteBehavior.Restrict);
+
+        builder.Property(x => x.VendorSnapshotName).IsRequired().HasMaxLength(200);
+        builder.Property(x => x.VendorSnapshotTaxNo).HasMaxLength(50);
+
+        builder.Property(x => x.Status)
+            .HasConversion<string>().HasMaxLength(20).IsRequired()
+            .HasDefaultValue(PurchaseInvoiceStatus.Draft);
+
+        foreach (var p in new[] { nameof(PurchaseInvoice.Subtotal), nameof(PurchaseInvoice.VatTotal), nameof(PurchaseInvoice.GrandTotal), nameof(PurchaseInvoice.PaidAmount), nameof(PurchaseInvoice.BalanceAmount) })
+            builder.Property<decimal>(p).HasPrecision(18, 4);
+        builder.Property(x => x.GlJournalNo).HasMaxLength(30);
+
+        builder.HasOne(x => x.Creator).WithMany().HasForeignKey(x => x.CreatedBy).OnDelete(DeleteBehavior.Restrict);
+        builder.Property(x => x.CreatedAt).IsRequired();
+        builder.Property(x => x.RowVersion).IsRowVersion();
+
+        builder.HasIndex(x => x.Status);
+        builder.HasIndex(x => x.VendorId);
+
+        builder.HasMany(x => x.Lines)
+            .WithOne(x => x.PurchaseInvoice)
+            .HasForeignKey(x => x.PurchaseInvoiceId)
+            .OnDelete(DeleteBehavior.Cascade);
+    }
+}
+
+public sealed class PurchaseInvoiceLineConfiguration : IEntityTypeConfiguration<PurchaseInvoiceLine>
+{
+    public void Configure(EntityTypeBuilder<PurchaseInvoiceLine> builder)
+    {
+        builder.ToTable("purchase_invoice_lines");
+        builder.HasKey(x => x.PurchaseInvoiceLineId);
+
+        builder.Property(x => x.Subtotal).HasPrecision(18, 4);
+        builder.Property(x => x.VatTotal).HasPrecision(18, 4);
+        builder.Property(x => x.LineTotal).HasPrecision(18, 4);
+
+        builder.HasOne(x => x.Grn)
+            .WithMany()
+            .HasForeignKey(x => x.GrnId)
+            .OnDelete(DeleteBehavior.Restrict);
+
+        // A GRN can be consolidated onto at most one active line at a time — cancelling the
+        // invoice removes its lines and frees the GRN (PurchaseInvoiceService.CancelAsync), so
+        // this stays enforceable rather than blocking a later re-invoice of the same GRN.
+        builder.HasIndex(x => x.GrnId).IsUnique();
+    }
+}
+
+public sealed class PurchaseInvoicePaymentConfiguration : IEntityTypeConfiguration<PurchaseInvoicePayment>
+{
+    public void Configure(EntityTypeBuilder<PurchaseInvoicePayment> builder)
+    {
+        builder.ToTable("purchase_invoice_payments");
+        builder.HasKey(p => p.PurchaseInvoicePaymentId);
+
+        builder.Property(p => p.Amount).HasPrecision(18, 4);
+        builder.Property(p => p.PaymentDate).IsRequired();
+        builder.Property(p => p.BankAccountName).IsRequired().HasMaxLength(200);
+        builder.Property(p => p.Reference).HasMaxLength(100);
+        builder.Property(p => p.GlJournalNo).HasMaxLength(30);
+        builder.Property(p => p.CreatedAt).IsRequired();
+
+        builder.HasOne(p => p.PurchaseInvoice).WithMany(x => x.Payments).HasForeignKey(p => p.PurchaseInvoiceId).OnDelete(DeleteBehavior.Restrict);
+        builder.HasOne(p => p.Creator).WithMany().HasForeignKey(p => p.CreatedBy).OnDelete(DeleteBehavior.Restrict);
+
+        builder.HasIndex(p => p.PurchaseInvoiceId);
+    }
+}

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

@@ -42,6 +42,7 @@ public sealed class SubNavItemConfiguration : IEntityTypeConfiguration<SubNavIte
             new SubNavItem { SubNavItemId = 18, NavItemId = 4, Code = "procurement.rfqs", Label = "RFQs", Href = "/dashboard/procurement/rfqs", SortOrder = 2 },
             new SubNavItem { SubNavItemId = 19, NavItemId = 4, Code = "procurement.purchase-orders", Label = "Purchase Orders", Href = "/dashboard/procurement/purchase-orders", SortOrder = 3 },
             new SubNavItem { SubNavItemId = 20, NavItemId = 4, Code = "procurement.purchase-returns", Label = "Purchase Returns", Href = "/dashboard/procurement/purchase-returns", SortOrder = 4 },
+            new SubNavItem { SubNavItemId = 28, NavItemId = 4, Code = "procurement.purchase-invoices", Label = "Purchase Invoices", Href = "/dashboard/procurement/purchase-invoices", SortOrder = 5 },
             new SubNavItem { SubNavItemId = 9, NavItemId = 11, Code = "ledgers.trial-balance", Label = "Trial Balance", Href = "/dashboard/ledgers/trial-balance", SortOrder = 1 },
             new SubNavItem { SubNavItemId = 10, NavItemId = 11, Code = "ledgers.balance-sheet", Label = "Balance Sheet", Href = "/dashboard/ledgers/balance-sheet", SortOrder = 2 },
             new SubNavItem { SubNavItemId = 11, NavItemId = 11, Code = "ledgers.general-ledger", Label = "General Ledger", Href = "/dashboard/ledgers/general-ledger", SortOrder = 3 },
@@ -56,7 +57,11 @@ public sealed class SubNavItemConfiguration : IEntityTypeConfiguration<SubNavIte
             new SubNavItem { SubNavItemId = 21, NavItemId = 12, Code = "accounts.cheque-books", Label = "Cheque Books", Href = "/dashboard/accounts/cheque-books", SortOrder = 2 },
             new SubNavItem { SubNavItemId = 22, NavItemId = 12, Code = "accounts.received-cheques", Label = "Received Cheques", Href = "/dashboard/accounts/received-cheques", SortOrder = 3 },
             // Production (NavItemId 14) children — mirror the sidebar order (AppSidebar.tsx).
-            new SubNavItem { SubNavItemId = 24, NavItemId = 14, Code = "production.templates", Label = "Templates", Href = "/dashboard/production/templates", SortOrder = 1 },
+            // ID 27 (not 24): 24 collides with settings.notification-config above — that ID was
+            // reused by mistake in migration 20260820100345, which upserts row 24 to become the
+            // notification-config item and silently overwrites this one. See migration
+            // FixProductionTemplatesSubNavItemIdConflict for the data repair.
+            new SubNavItem { SubNavItemId = 27, NavItemId = 14, Code = "production.templates", Label = "Templates", Href = "/dashboard/production/templates", SortOrder = 1 },
             new SubNavItem { SubNavItemId = 25, NavItemId = 14, Code = "production.runs", Label = "Runs", Href = "/dashboard/production/runs", SortOrder = 2 },
             new SubNavItem { SubNavItemId = 26, NavItemId = 14, Code = "production.produced", Label = "Produced", Href = "/dashboard/production/produced", SortOrder = 3 }
         );

Backend/ERPCore/Infra/Persistence/ErpDbContext.cs

@@ -66,7 +66,11 @@ public class ErpDbContext : DbContext
     // --- Goods Receipt (docs/10 Part C.3) ---
     public DbSet<Grn> Grns => Set<Grn>();
     public DbSet<GrnLine> GrnLines => Set<GrnLine>();
-    public DbSet<GrnPayment> GrnPayments => Set<GrnPayment>();
+
+    // --- Purchase Invoices (vendor invoices consolidating Confirmed GRNs) ---
+    public DbSet<PurchaseInvoice> PurchaseInvoices => Set<PurchaseInvoice>();
+    public DbSet<PurchaseInvoiceLine> PurchaseInvoiceLines => Set<PurchaseInvoiceLine>();
+    public DbSet<PurchaseInvoicePayment> PurchaseInvoicePayments => Set<PurchaseInvoicePayment>();
 
     // --- Batch / Serial (docs/10 Part C.4) ---
     public DbSet<Batch> Batches => Set<Batch>();

Backend/ERPCore/Migrations/20260825000000_FixProductionTemplatesSubNavItemIdConflict.Designer.cs

@@ -0,0 +1,24 @@
+// <auto-generated />
+using ERPCore.Infra.Persistence;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Infrastructure;
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace ERPCore.Migrations
+{
+    [DbContext(typeof(ErpDbContext))]
+    [Migration("20260825000000_FixProductionTemplatesSubNavItemIdConflict")]
+    partial class FixProductionTemplatesSubNavItemIdConflict
+    {
+        /// <inheritdoc />
+        protected override void BuildTargetModel(ModelBuilder modelBuilder)
+        {
+            // This migration only repairs seed row data via raw SQL — no entity/column shape
+            // changes — so it does not redeclare the full model here. The single source of
+            // truth for scaffolding future migrations is ErpDbContextModelSnapshot.cs, which
+            // already reflects this fix (production.templates seeded at SubNavItemId 27).
+        }
+    }
+}

Backend/ERPCore/Migrations/20260825000000_FixProductionTemplatesSubNavItemIdConflict.cs

@@ -0,0 +1,46 @@
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace ERPCore.Migrations
+{
+    /// <summary>
+    /// Repairs a collision baked into migration history: 20260818090139_AddProductionNavPermissions
+    /// inserted "production.templates" as sub_nav_items row 24, then
+    /// 20260820100345_AddNotificationConfigModulePreferences reused the same literal id 24 for
+    /// "settings.notification-config" via a raw-SQL <c>INSERT ... ON CONFLICT ("SubNavItemId") DO
+    /// UPDATE</c>, silently overwriting the production.templates row instead of inserting a new
+    /// one. Row 24 now correctly holds notification-config; this migration re-creates the lost
+    /// production.templates row under a fresh id (27, matching the corrected seed data in
+    /// SubNavItemConfiguration/PermissionConfiguration) and repoints the NAV:production.templates
+    /// permission (id 36) at it.
+    /// </summary>
+    public partial class FixProductionTemplatesSubNavItemIdConflict : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.Sql("""
+                INSERT INTO sub_nav_items ("SubNavItemId", "NavItemId", "Code", "Href", "Icon", "Label", "SortOrder")
+                VALUES (27, 14, 'production.templates', '/dashboard/production/templates', NULL, 'Templates', 1)
+                ON CONFLICT ("SubNavItemId") DO NOTHING;
+                """);
+
+            migrationBuilder.Sql("""
+                UPDATE permissions SET "SubNavItemId" = 27 WHERE "PermissionId" = 36;
+                """);
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.Sql("""
+                UPDATE permissions SET "SubNavItemId" = 24 WHERE "PermissionId" = 36;
+                """);
+
+            migrationBuilder.Sql("""
+                DELETE FROM sub_nav_items WHERE "SubNavItemId" = 27;
+                """);
+        }
+    }
+}

Backend/ERPCore/Migrations/20260831060800_AddPurchaseInvoices.cs

@@ -0,0 +1,303 @@
+using System;
+using Microsoft.EntityFrameworkCore.Migrations;
+using Npgsql.EntityFrameworkCore.PostgreSQL.Metadata;
+
+#nullable disable
+
+namespace ERPCore.Migrations
+{
+    /// <inheritdoc />
+    public partial class AddPurchaseInvoices : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropTable(
+                name: "grn_payments");
+
+            migrationBuilder.DropColumn(
+                name: "BalanceAmount",
+                table: "grns");
+
+            migrationBuilder.DropColumn(
+                name: "PaidAmount",
+                table: "grns");
+
+            migrationBuilder.AddColumn<int>(
+                name: "PurchaseInvoiceId",
+                table: "grns",
+                type: "integer",
+                nullable: true);
+
+            migrationBuilder.CreateTable(
+                name: "purchase_invoices",
+                columns: table => new
+                {
+                    PurchaseInvoiceId = table.Column<int>(type: "integer", nullable: false)
+                        .Annotation("Npgsql:ValueGenerationStrategy", NpgsqlValueGenerationStrategy.IdentityByDefaultColumn),
+                    DocNo = table.Column<string>(type: "character varying(30)", maxLength: 30, nullable: false),
+                    VendorInvoiceNo = table.Column<string>(type: "character varying(50)", maxLength: 50, nullable: false),
+                    VendorInvoiceDate = table.Column<DateTime>(type: "timestamp with time zone", nullable: false),
+                    VendorId = table.Column<int>(type: "integer", nullable: false),
+                    VendorSnapshotName = table.Column<string>(type: "character varying(200)", maxLength: 200, nullable: false),
+                    VendorSnapshotTaxNo = table.Column<string>(type: "character varying(50)", maxLength: 50, nullable: true),
+                    Status = table.Column<string>(type: "character varying(20)", maxLength: 20, nullable: false, defaultValue: "Draft"),
+                    Subtotal = table.Column<decimal>(type: "numeric(18,4)", precision: 18, scale: 4, nullable: false),
+                    VatTotal = table.Column<decimal>(type: "numeric(18,4)", precision: 18, scale: 4, nullable: false),
+                    GrandTotal = table.Column<decimal>(type: "numeric(18,4)", precision: 18, scale: 4, nullable: false),
+                    PaidAmount = table.Column<decimal>(type: "numeric(18,4)", precision: 18, scale: 4, nullable: false),
+                    BalanceAmount = table.Column<decimal>(type: "numeric(18,4)", precision: 18, scale: 4, nullable: false),
+                    GlJournalNo = table.Column<string>(type: "character varying(30)", maxLength: 30, nullable: true),
+                    GlPostedAt = table.Column<DateTime>(type: "timestamp with time zone", nullable: true),
+                    CreatedBy = table.Column<int>(type: "integer", nullable: false),
+                    CreatedAt = table.Column<DateTime>(type: "timestamp with time zone", nullable: false),
+                    UpdatedAt = 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_purchase_invoices", x => x.PurchaseInvoiceId);
+                    table.ForeignKey(
+                        name: "FK_purchase_invoices_users_CreatedBy",
+                        column: x => x.CreatedBy,
+                        principalTable: "users",
+                        principalColumn: "UserId",
+                        onDelete: ReferentialAction.Restrict);
+                    table.ForeignKey(
+                        name: "FK_purchase_invoices_vendors_VendorId",
+                        column: x => x.VendorId,
+                        principalTable: "vendors",
+                        principalColumn: "VendorId",
+                        onDelete: ReferentialAction.Restrict);
+                });
+
+            migrationBuilder.CreateTable(
+                name: "purchase_invoice_lines",
+                columns: table => new
+                {
+                    PurchaseInvoiceLineId = table.Column<int>(type: "integer", nullable: false)
+                        .Annotation("Npgsql:ValueGenerationStrategy", NpgsqlValueGenerationStrategy.IdentityByDefaultColumn),
+                    PurchaseInvoiceId = table.Column<int>(type: "integer", nullable: false),
+                    GrnId = table.Column<int>(type: "integer", nullable: false),
+                    Subtotal = table.Column<decimal>(type: "numeric(18,4)", precision: 18, scale: 4, nullable: false),
+                    VatTotal = table.Column<decimal>(type: "numeric(18,4)", precision: 18, scale: 4, nullable: false),
+                    LineTotal = table.Column<decimal>(type: "numeric(18,4)", precision: 18, scale: 4, nullable: false)
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("PK_purchase_invoice_lines", x => x.PurchaseInvoiceLineId);
+                    table.ForeignKey(
+                        name: "FK_purchase_invoice_lines_grns_GrnId",
+                        column: x => x.GrnId,
+                        principalTable: "grns",
+                        principalColumn: "GrnId",
+                        onDelete: ReferentialAction.Restrict);
+                    table.ForeignKey(
+                        name: "FK_purchase_invoice_lines_purchase_invoices_PurchaseInvoiceId",
+                        column: x => x.PurchaseInvoiceId,
+                        principalTable: "purchase_invoices",
+                        principalColumn: "PurchaseInvoiceId",
+                        onDelete: ReferentialAction.Cascade);
+                });
+
+            migrationBuilder.CreateTable(
+                name: "purchase_invoice_payments",
+                columns: table => new
+                {
+                    PurchaseInvoicePaymentId = table.Column<int>(type: "integer", nullable: false)
+                        .Annotation("Npgsql:ValueGenerationStrategy", NpgsqlValueGenerationStrategy.IdentityByDefaultColumn),
+                    PurchaseInvoiceId = table.Column<int>(type: "integer", nullable: false),
+                    Amount = table.Column<decimal>(type: "numeric(18,4)", precision: 18, scale: 4, nullable: false),
+                    PaymentDate = table.Column<DateTime>(type: "timestamp with time zone", nullable: false),
+                    GlBankAccountId = table.Column<long>(type: "bigint", nullable: false),
+                    BankAccountName = table.Column<string>(type: "character varying(200)", maxLength: 200, nullable: false),
+                    Reference = table.Column<string>(type: "character varying(100)", maxLength: 100, nullable: true),
+                    GlJournalNo = table.Column<string>(type: "character varying(30)", maxLength: 30, nullable: true),
+                    CreatedBy = table.Column<int>(type: "integer", nullable: false),
+                    CreatedAt = table.Column<DateTime>(type: "timestamp with time zone", nullable: false)
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("PK_purchase_invoice_payments", x => x.PurchaseInvoicePaymentId);
+                    table.ForeignKey(
+                        name: "FK_purchase_invoice_payments_purchase_invoices_PurchaseInvoice~",
+                        column: x => x.PurchaseInvoiceId,
+                        principalTable: "purchase_invoices",
+                        principalColumn: "PurchaseInvoiceId",
+                        onDelete: ReferentialAction.Restrict);
+                    table.ForeignKey(
+                        name: "FK_purchase_invoice_payments_users_CreatedBy",
+                        column: x => x.CreatedBy,
+                        principalTable: "users",
+                        principalColumn: "UserId",
+                        onDelete: ReferentialAction.Restrict);
+                });
+
+            migrationBuilder.InsertData(
+                table: "sub_nav_items",
+                columns: new[] { "SubNavItemId", "Code", "Href", "Icon", "Label", "NavItemId", "SortOrder" },
+                values: new object[] { 28, "procurement.purchase-invoices", "/dashboard/procurement/purchase-invoices", null, "Purchase Invoices", 4, 5 });
+
+            migrationBuilder.InsertData(
+                table: "permissions",
+                columns: new[] { "PermissionId", "Code", "NavItemId", "SubNavItemId" },
+                values: new object[] { 39, "NAV:procurement.purchase-invoices", null, 28 });
+
+            migrationBuilder.CreateIndex(
+                name: "IX_grns_PurchaseInvoiceId",
+                table: "grns",
+                column: "PurchaseInvoiceId");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_purchase_invoice_lines_GrnId",
+                table: "purchase_invoice_lines",
+                column: "GrnId",
+                unique: true);
+
+            migrationBuilder.CreateIndex(
+                name: "IX_purchase_invoice_lines_PurchaseInvoiceId",
+                table: "purchase_invoice_lines",
+                column: "PurchaseInvoiceId");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_purchase_invoice_payments_CreatedBy",
+                table: "purchase_invoice_payments",
+                column: "CreatedBy");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_purchase_invoice_payments_PurchaseInvoiceId",
+                table: "purchase_invoice_payments",
+                column: "PurchaseInvoiceId");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_purchase_invoices_CreatedBy",
+                table: "purchase_invoices",
+                column: "CreatedBy");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_purchase_invoices_DocNo",
+                table: "purchase_invoices",
+                column: "DocNo",
+                unique: true);
+
+            migrationBuilder.CreateIndex(
+                name: "IX_purchase_invoices_Status",
+                table: "purchase_invoices",
+                column: "Status");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_purchase_invoices_VendorId",
+                table: "purchase_invoices",
+                column: "VendorId");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_purchase_invoices_VendorId_VendorInvoiceNo",
+                table: "purchase_invoices",
+                columns: new[] { "VendorId", "VendorInvoiceNo" });
+
+            migrationBuilder.AddForeignKey(
+                name: "FK_grns_purchase_invoices_PurchaseInvoiceId",
+                table: "grns",
+                column: "PurchaseInvoiceId",
+                principalTable: "purchase_invoices",
+                principalColumn: "PurchaseInvoiceId",
+                onDelete: ReferentialAction.Restrict);
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropForeignKey(
+                name: "FK_grns_purchase_invoices_PurchaseInvoiceId",
+                table: "grns");
+
+            migrationBuilder.DropTable(
+                name: "purchase_invoice_lines");
+
+            migrationBuilder.DropTable(
+                name: "purchase_invoice_payments");
+
+            migrationBuilder.DropTable(
+                name: "purchase_invoices");
+
+            migrationBuilder.DropIndex(
+                name: "IX_grns_PurchaseInvoiceId",
+                table: "grns");
+
+            migrationBuilder.DeleteData(
+                table: "permissions",
+                keyColumn: "PermissionId",
+                keyValue: 39);
+
+            migrationBuilder.DeleteData(
+                table: "sub_nav_items",
+                keyColumn: "SubNavItemId",
+                keyValue: 28);
+
+            migrationBuilder.DropColumn(
+                name: "PurchaseInvoiceId",
+                table: "grns");
+
+            migrationBuilder.AddColumn<decimal>(
+                name: "BalanceAmount",
+                table: "grns",
+                type: "numeric(18,4)",
+                precision: 18,
+                scale: 4,
+                nullable: false,
+                defaultValue: 0m);
+
+            migrationBuilder.AddColumn<decimal>(
+                name: "PaidAmount",
+                table: "grns",
+                type: "numeric(18,4)",
+                precision: 18,
+                scale: 4,
+                nullable: false,
+                defaultValue: 0m);
+
+            migrationBuilder.CreateTable(
+                name: "grn_payments",
+                columns: table => new
+                {
+                    GrnPaymentId = table.Column<int>(type: "integer", nullable: false)
+                        .Annotation("Npgsql:ValueGenerationStrategy", NpgsqlValueGenerationStrategy.IdentityByDefaultColumn),
+                    CreatedBy = table.Column<int>(type: "integer", nullable: false),
+                    GrnId = table.Column<int>(type: "integer", nullable: false),
+                    Amount = table.Column<decimal>(type: "numeric(18,4)", precision: 18, scale: 4, nullable: false),
+                    BankAccountName = table.Column<string>(type: "character varying(200)", maxLength: 200, nullable: false),
+                    CreatedAt = table.Column<DateTime>(type: "timestamp with time zone", nullable: false),
+                    GlBankAccountId = table.Column<long>(type: "bigint", nullable: false),
+                    GlJournalNo = table.Column<string>(type: "character varying(30)", maxLength: 30, nullable: true),
+                    PaymentDate = table.Column<DateTime>(type: "timestamp with time zone", nullable: false),
+                    Reference = table.Column<string>(type: "character varying(100)", maxLength: 100, nullable: true)
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("PK_grn_payments", x => x.GrnPaymentId);
+                    table.ForeignKey(
+                        name: "FK_grn_payments_grns_GrnId",
+                        column: x => x.GrnId,
+                        principalTable: "grns",
+                        principalColumn: "GrnId",
+                        onDelete: ReferentialAction.Restrict);
+                    table.ForeignKey(
+                        name: "FK_grn_payments_users_CreatedBy",
+                        column: x => x.CreatedBy,
+                        principalTable: "users",
+                        principalColumn: "UserId",
+                        onDelete: ReferentialAction.Restrict);
+                });
+
+            migrationBuilder.CreateIndex(
+                name: "IX_grn_payments_CreatedBy",
+                table: "grn_payments",
+                column: "CreatedBy");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_grn_payments_GrnId",
+                table: "grn_payments",
+                column: "GrnId");
+        }
+    }
+}

Backend/ERPCore/Migrations/ErpDbContextModelSnapshot.cs

@@ -1411,10 +1411,6 @@ namespace ERPCore.Migrations
 
                     NpgsqlPropertyBuilderExtensions.UseIdentityByDefaultColumn(b.Property<int>("GrnId"));
 
-                    b.Property<decimal>("BalanceAmount")
-                        .HasPrecision(18, 4)
-                        .HasColumnType("numeric(18,4)");
-
                     b.Property<DateTime>("CreatedAt")
                         .HasColumnType("timestamp with time zone");
 
@@ -1433,16 +1429,15 @@ namespace ERPCore.Migrations
                     b.Property<DateTime?>("GlPostedAt")
                         .HasColumnType("timestamp with time zone");
 
-                    b.Property<decimal>("PaidAmount")
-                        .HasPrecision(18, 4)
-                        .HasColumnType("numeric(18,4)");
-
                     b.Property<int?>("PoId")
                         .HasColumnType("integer");
 
                     b.Property<DateTime?>("PostedAt")
                         .HasColumnType("timestamp with time zone");
 
+                    b.Property<int?>("PurchaseInvoiceId")
+                        .HasColumnType("integer");
+
                     b.Property<uint>("RowVersion")
                         .IsConcurrencyToken()
                         .ValueGeneratedOnAddOrUpdate()
@@ -1469,6 +1464,8 @@ namespace ERPCore.Migrations
 
                     b.HasIndex("PoId");
 
+                    b.HasIndex("PurchaseInvoiceId");
+
                     b.HasIndex("Status");
 
                     b.HasIndex("VendorId");
@@ -1584,55 +1581,6 @@ namespace ERPCore.Migrations
                     b.ToTable("grn_line_warranty_numbers", (string)null);
                 });
 
-            modelBuilder.Entity("ERPCore.Domain.Entities.GrnPayment", b =>
-                {
-                    b.Property<int>("GrnPaymentId")
-                        .ValueGeneratedOnAdd()
-                        .HasColumnType("integer");
-
-                    NpgsqlPropertyBuilderExtensions.UseIdentityByDefaultColumn(b.Property<int>("GrnPaymentId"));
-
-                    b.Property<decimal>("Amount")
-                        .HasPrecision(18, 4)
-                        .HasColumnType("numeric(18,4)");
-
-                    b.Property<string>("BankAccountName")
-                        .IsRequired()
-                        .HasMaxLength(200)
-                        .HasColumnType("character varying(200)");
-
-                    b.Property<DateTime>("CreatedAt")
-                        .HasColumnType("timestamp with time zone");
-
-                    b.Property<int>("CreatedBy")
-                        .HasColumnType("integer");
-
-                    b.Property<long>("GlBankAccountId")
-                        .HasColumnType("bigint");
-
-                    b.Property<string>("GlJournalNo")
-                        .HasMaxLength(30)
-                        .HasColumnType("character varying(30)");
-
-                    b.Property<int>("GrnId")
-                        .HasColumnType("integer");
-
-                    b.Property<DateTime>("PaymentDate")
-                        .HasColumnType("timestamp with time zone");
-
-                    b.Property<string>("Reference")
-                        .HasMaxLength(100)
-                        .HasColumnType("character varying(100)");
-
-                    b.HasKey("GrnPaymentId");
-
-                    b.HasIndex("CreatedBy");
-
-                    b.HasIndex("GrnId");
-
-                    b.ToTable("grn_payments", (string)null);
-                });
-
             modelBuilder.Entity("ERPCore.Domain.Entities.HrDocumentType", b =>
                 {
                     b.Property<int>("HrDocumentTypeId")
@@ -2976,7 +2924,7 @@ namespace ERPCore.Migrations
                         {
                             PermissionId = 36,
                             Code = "NAV:production.templates",
-                            SubNavItemId = 24
+                            SubNavItemId = 27
                         },
                         new
                         {
@@ -2989,6 +2937,12 @@ namespace ERPCore.Migrations
                             PermissionId = 38,
                             Code = "NAV:production.produced",
                             SubNavItemId = 26
+                        },
+                        new
+                        {
+                            PermissionId = 39,
+                            Code = "NAV:procurement.purchase-invoices",
+                            SubNavItemId = 28
                         });
                 });
 
@@ -3228,6 +3182,189 @@ namespace ERPCore.Migrations
                     b.ToTable("production_templates", (string)null);
                 });
 
+            modelBuilder.Entity("ERPCore.Domain.Entities.PurchaseInvoice", b =>
+                {
+                    b.Property<int>("PurchaseInvoiceId")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("integer");
+
+                    NpgsqlPropertyBuilderExtensions.UseIdentityByDefaultColumn(b.Property<int>("PurchaseInvoiceId"));
+
+                    b.Property<decimal>("BalanceAmount")
+                        .HasPrecision(18, 4)
+                        .HasColumnType("numeric(18,4)");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<int>("CreatedBy")
+                        .HasColumnType("integer");
+
+                    b.Property<string>("DocNo")
+                        .IsRequired()
+                        .HasMaxLength(30)
+                        .HasColumnType("character varying(30)");
+
+                    b.Property<string>("GlJournalNo")
+                        .HasMaxLength(30)
+                        .HasColumnType("character varying(30)");
+
+                    b.Property<DateTime?>("GlPostedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<decimal>("GrandTotal")
+                        .HasPrecision(18, 4)
+                        .HasColumnType("numeric(18,4)");
+
+                    b.Property<decimal>("PaidAmount")
+                        .HasPrecision(18, 4)
+                        .HasColumnType("numeric(18,4)");
+
+                    b.Property<uint>("RowVersion")
+                        .IsConcurrencyToken()
+                        .ValueGeneratedOnAddOrUpdate()
+                        .HasColumnType("xid")
+                        .HasColumnName("xmin");
+
+                    b.Property<string>("Status")
+                        .IsRequired()
+                        .ValueGeneratedOnAdd()
+                        .HasMaxLength(20)
+                        .HasColumnType("character varying(20)")
+                        .HasDefaultValue("Draft");
+
+                    b.Property<decimal>("Subtotal")
+                        .HasPrecision(18, 4)
+                        .HasColumnType("numeric(18,4)");
+
+                    b.Property<DateTime?>("UpdatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<decimal>("VatTotal")
+                        .HasPrecision(18, 4)
+                        .HasColumnType("numeric(18,4)");
+
+                    b.Property<int>("VendorId")
+                        .HasColumnType("integer");
+
+                    b.Property<DateTime>("VendorInvoiceDate")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<string>("VendorInvoiceNo")
+                        .IsRequired()
+                        .HasMaxLength(50)
+                        .HasColumnType("character varying(50)");
+
+                    b.Property<string>("VendorSnapshotName")
+                        .IsRequired()
+                        .HasMaxLength(200)
+                        .HasColumnType("character varying(200)");
+
+                    b.Property<string>("VendorSnapshotTaxNo")
+                        .HasMaxLength(50)
+                        .HasColumnType("character varying(50)");
+
+                    b.HasKey("PurchaseInvoiceId");
+
+                    b.HasIndex("CreatedBy");
+
+                    b.HasIndex("DocNo")
+                        .IsUnique();
+
+                    b.HasIndex("Status");
+
+                    b.HasIndex("VendorId");
+
+                    b.HasIndex("VendorId", "VendorInvoiceNo");
+
+                    b.ToTable("purchase_invoices", (string)null);
+                });
+
+            modelBuilder.Entity("ERPCore.Domain.Entities.PurchaseInvoiceLine", b =>
+                {
+                    b.Property<int>("PurchaseInvoiceLineId")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("integer");
+
+                    NpgsqlPropertyBuilderExtensions.UseIdentityByDefaultColumn(b.Property<int>("PurchaseInvoiceLineId"));
+
+                    b.Property<int>("GrnId")
+                        .HasColumnType("integer");
+
+                    b.Property<decimal>("LineTotal")
+                        .HasPrecision(18, 4)
+                        .HasColumnType("numeric(18,4)");
+
+                    b.Property<int>("PurchaseInvoiceId")
+                        .HasColumnType("integer");
+
+                    b.Property<decimal>("Subtotal")
+                        .HasPrecision(18, 4)
+                        .HasColumnType("numeric(18,4)");
+
+                    b.Property<decimal>("VatTotal")
+                        .HasPrecision(18, 4)
+                        .HasColumnType("numeric(18,4)");
+
+                    b.HasKey("PurchaseInvoiceLineId");
+
+                    b.HasIndex("GrnId")
+                        .IsUnique();
+
+                    b.HasIndex("PurchaseInvoiceId");
+
+                    b.ToTable("purchase_invoice_lines", (string)null);
+                });
+
+            modelBuilder.Entity("ERPCore.Domain.Entities.PurchaseInvoicePayment", b =>
+                {
+                    b.Property<int>("PurchaseInvoicePaymentId")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("integer");
+
+                    NpgsqlPropertyBuilderExtensions.UseIdentityByDefaultColumn(b.Property<int>("PurchaseInvoicePaymentId"));
+
+                    b.Property<decimal>("Amount")
+                        .HasPrecision(18, 4)
+                        .HasColumnType("numeric(18,4)");
+
+                    b.Property<string>("BankAccountName")
+                        .IsRequired()
+                        .HasMaxLength(200)
+                        .HasColumnType("character varying(200)");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<int>("CreatedBy")
+                        .HasColumnType("integer");
+
+                    b.Property<long>("GlBankAccountId")
+                        .HasColumnType("bigint");
+
+                    b.Property<string>("GlJournalNo")
+                        .HasMaxLength(30)
+                        .HasColumnType("character varying(30)");
+
+                    b.Property<DateTime>("PaymentDate")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<int>("PurchaseInvoiceId")
+                        .HasColumnType("integer");
+
+                    b.Property<string>("Reference")
+                        .HasMaxLength(100)
+                        .HasColumnType("character varying(100)");
+
+                    b.HasKey("PurchaseInvoicePaymentId");
+
+                    b.HasIndex("CreatedBy");
+
+                    b.HasIndex("PurchaseInvoiceId");
+
+                    b.ToTable("purchase_invoice_payments", (string)null);
+                });
+
             modelBuilder.Entity("ERPCore.Domain.Entities.PurchaseOrder", b =>
                 {
                     b.Property<int>("PoId")
@@ -5337,6 +5474,16 @@ namespace ERPCore.Migrations
                             Status = "Active"
                         },
                         new
+                        {
+                            SubNavItemId = 28,
+                            Code = "procurement.purchase-invoices",
+                            Href = "/dashboard/procurement/purchase-invoices",
+                            Label = "Purchase Invoices",
+                            NavItemId = 4,
+                            SortOrder = 5,
+                            Status = "Active"
+                        },
+                        new
                         {
                             SubNavItemId = 9,
                             Code = "ledgers.trial-balance",
@@ -5438,7 +5585,7 @@ namespace ERPCore.Migrations
                         },
                         new
                         {
-                            SubNavItemId = 24,
+                            SubNavItemId = 27,
                             Code = "production.templates",
                             Href = "/dashboard/production/templates",
                             Label = "Templates",
@@ -6176,6 +6323,11 @@ namespace ERPCore.Migrations
                         .HasForeignKey("PoId")
                         .OnDelete(DeleteBehavior.Restrict);
 
+                    b.HasOne("ERPCore.Domain.Entities.PurchaseInvoice", "PurchaseInvoice")
+                        .WithMany()
+                        .HasForeignKey("PurchaseInvoiceId")
+                        .OnDelete(DeleteBehavior.Restrict);
+
                     b.HasOne("ERPCore.Domain.Entities.Vendor", "Vendor")
                         .WithMany()
                         .HasForeignKey("VendorId")
@@ -6190,6 +6342,8 @@ namespace ERPCore.Migrations
 
                     b.Navigation("Creator");
 
+                    b.Navigation("PurchaseInvoice");
+
                     b.Navigation("PurchaseOrder");
 
                     b.Navigation("Vendor");
@@ -6248,25 +6402,6 @@ namespace ERPCore.Migrations
                     b.Navigation("GrnLine");
                 });
 
-            modelBuilder.Entity("ERPCore.Domain.Entities.GrnPayment", b =>
-                {
-                    b.HasOne("ERPCore.Domain.Entities.User", "Creator")
-                        .WithMany()
-                        .HasForeignKey("CreatedBy")
-                        .OnDelete(DeleteBehavior.Restrict)
-                        .IsRequired();
-
-                    b.HasOne("ERPCore.Domain.Entities.Grn", "Grn")
-                        .WithMany("Payments")
-                        .HasForeignKey("GrnId")
-                        .OnDelete(DeleteBehavior.Restrict)
-                        .IsRequired();
-
-                    b.Navigation("Creator");
-
-                    b.Navigation("Grn");
-                });
-
             modelBuilder.Entity("ERPCore.Domain.Entities.Item", b =>
                 {
                     b.HasOne("ERPCore.Domain.Entities.Uom", "BaseUom")
@@ -6567,6 +6702,63 @@ namespace ERPCore.Migrations
                     b.Navigation("Creator");
                 });
 
+            modelBuilder.Entity("ERPCore.Domain.Entities.PurchaseInvoice", b =>
+                {
+                    b.HasOne("ERPCore.Domain.Entities.User", "Creator")
+                        .WithMany()
+                        .HasForeignKey("CreatedBy")
+                        .OnDelete(DeleteBehavior.Restrict)
+                        .IsRequired();
+
+                    b.HasOne("ERPCore.Domain.Entities.Vendor", "Vendor")
+                        .WithMany()
+                        .HasForeignKey("VendorId")
+                        .OnDelete(DeleteBehavior.Restrict)
+                        .IsRequired();
+
+                    b.Navigation("Creator");
+
+                    b.Navigation("Vendor");
+                });
+
+            modelBuilder.Entity("ERPCore.Domain.Entities.PurchaseInvoiceLine", b =>
+                {
+                    b.HasOne("ERPCore.Domain.Entities.Grn", "Grn")
+                        .WithMany()
+                        .HasForeignKey("GrnId")
+                        .OnDelete(DeleteBehavior.Restrict)
+                        .IsRequired();
+
+                    b.HasOne("ERPCore.Domain.Entities.PurchaseInvoice", "PurchaseInvoice")
+                        .WithMany("Lines")
+                        .HasForeignKey("PurchaseInvoiceId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("Grn");
+
+                    b.Navigation("PurchaseInvoice");
+                });
+
+            modelBuilder.Entity("ERPCore.Domain.Entities.PurchaseInvoicePayment", b =>
+                {
+                    b.HasOne("ERPCore.Domain.Entities.User", "Creator")
+                        .WithMany()
+                        .HasForeignKey("CreatedBy")
+                        .OnDelete(DeleteBehavior.Restrict)
+                        .IsRequired();
+
+                    b.HasOne("ERPCore.Domain.Entities.PurchaseInvoice", "PurchaseInvoice")
+                        .WithMany("Payments")
+                        .HasForeignKey("PurchaseInvoiceId")
+                        .OnDelete(DeleteBehavior.Restrict)
+                        .IsRequired();
+
+                    b.Navigation("Creator");
+
+                    b.Navigation("PurchaseInvoice");
+                });
+
             modelBuilder.Entity("ERPCore.Domain.Entities.PurchaseOrder", b =>
                 {
                     b.HasOne("ERPCore.Domain.Entities.User", "Creator")
@@ -7516,8 +7708,6 @@ namespace ERPCore.Migrations
             modelBuilder.Entity("ERPCore.Domain.Entities.Grn", b =>
                 {
                     b.Navigation("Lines");
-
-                    b.Navigation("Payments");
                 });
 
             modelBuilder.Entity("ERPCore.Domain.Entities.GrnLine", b =>
@@ -7568,6 +7758,13 @@ namespace ERPCore.Migrations
                     b.Navigation("Stages");
                 });
 
+            modelBuilder.Entity("ERPCore.Domain.Entities.PurchaseInvoice", b =>
+                {
+                    b.Navigation("Lines");
+
+                    b.Navigation("Payments");
+                });
+
             modelBuilder.Entity("ERPCore.Domain.Entities.PurchaseOrder", b =>
                 {
                     b.Navigation("Lines");

Backend/ERPCore/Program.cs

@@ -105,7 +105,10 @@ builder.Services.AddScoped<IItemMeasure, ItemMeasure>();
 builder.Services.AddScoped<IFifoCostingService, FifoCostingService>();
 builder.Services.AddScoped<IStockService, StockService>();
 builder.Services.AddScoped<IGrnService, GrnService>();
-builder.Services.AddScoped<IGrnPaymentService, GrnPaymentService>();
+
+// Purchase invoices (vendor invoices consolidating Confirmed GRNs)
+builder.Services.AddScoped<IPurchaseInvoiceService, PurchaseInvoiceService>();
+builder.Services.AddScoped<IPurchaseInvoicePaymentService, PurchaseInvoicePaymentService>();
 
 // Sales (Phase 1)
 builder.Services.AddScoped<ISalesPricingService, SalesPricingService>();

Backend/ERPCore/Services/GrnPaymentService.cs

@@ -1,120 +0,0 @@
-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.Gl;
-using ERPCore.Services.Interfaces;
-using ERPCore.System.Errors;
-using Microsoft.EntityFrameworkCore;
-
-namespace ERPCore.Services;
-
-/// <summary>
-/// Vendor payments against a confirmed GRN. Multiple installments are allowed until
-/// <see cref="Grn.BalanceAmount"/> reaches zero. Each payment posts its own real GL
-/// journal entry (Debit GRN Clearing / Credit the selected bank-or-cash account) before
-/// being recorded, using the same call-GL-before-commit pattern as <see cref="GrnService.ConfirmAsync"/>
-/// so a rejected/unreachable GL post rolls back the whole payment atomically.
-/// </summary>
-public sealed class GrnPaymentService : IGrnPaymentService
-{
-    private readonly IRepository<Grn> _grns;
-    private readonly IRepository<GrnPayment> _payments;
-    private readonly IGeneralLedgerService _gl;
-    private readonly ICurrentUser _currentUser;
-    private readonly IUnitOfWork _uow;
-    private readonly string _glClearingAccountCode;
-
-    public GrnPaymentService(
-        IRepository<Grn> grns, IRepository<GrnPayment> payments, IGeneralLedgerService gl,
-        ICurrentUser currentUser, IUnitOfWork uow, IConfiguration configuration)
-    {
-        _grns = grns;
-        _payments = payments;
-        _gl = gl;
-        _currentUser = currentUser;
-        _uow = uow;
-        _glClearingAccountCode = configuration["Grn:GlClearingAccountCode"] ?? string.Empty;
-    }
-
-    public async Task<GrnPaymentDto> PayAsync(int grnId, CreateGrnPaymentRequest request, CancellationToken ct = default)
-    {
-        var grn = await _grns.Query().FirstOrDefaultAsync(g => g.GrnId == grnId, ct)
-            ?? throw new NotFoundException($"GRN {grnId} was not found.");
-
-        if (grn.Status == GrnStatus.Draft)
-            throw new DomainException(ErrorCodes.GrnNotPayable, $"GRN {grnId} must be confirmed before it can be paid.", 409);
-        if (request.Amount > grn.BalanceAmount)
-            throw new DomainException(ErrorCodes.GrnPaymentExceedsBalance,
-                $"Payment amount {request.Amount} exceeds the remaining balance {grn.BalanceAmount}.", 400);
-
-        var accounts = await _gl.ListBankAccountsAsync(ct);
-        var account = accounts.FirstOrDefault(a => a.AccountId == request.GlBankAccountId)
-            ?? throw new DomainException(ErrorCodes.GrnBankAccountNotFound, $"Bank/cash account {request.GlBankAccountId} was not found.", 404);
-
-        var actor = _currentUser.AuditUserId;
-        var now = DateTime.UtcNow;
-
-        var payment = await _uow.ExecuteInTransactionAsync(async token =>
-        {
-            // Same atomicity approach as GrnService.ConfirmAsync: post to GL first, inside
-            // this transaction, before anything is committed — a GL rejection/timeout rolls
-            // the whole payment back with no partial local state.
-            var period = await _gl.GetPeriodByDateAsync(DateOnly.FromDateTime(now), token);
-            var posted = await _gl.PostJournalEntryAsync(new GlJournalEntryRequest
-            {
-                PeriodId = period.PeriodId,
-                EntryDate = DateOnly.FromDateTime(now),
-                SourceModule = "GRN_PAYMENT",
-                Reference = grn.DocNo,
-                Narration = $"Payment against GRN {grn.DocNo}",
-                Lines =
-                [
-                    new GlJournalEntryLineRequest(_glClearingAccountCode, request.Amount, 0m, $"Payment against GRN {grn.DocNo}"),
-                    new GlJournalEntryLineRequest(account.GlAccountCode, 0m, request.Amount, $"Payment against GRN {grn.DocNo}")
-                ]
-            }, token);
-
-            var entity = new GrnPayment
-            {
-                GrnId = grn.GrnId,
-                Amount = request.Amount,
-                PaymentDate = now,
-                GlBankAccountId = account.AccountId,
-                BankAccountName = account.AccountName,
-                Reference = request.Reference,
-                GlJournalNo = posted.JournalNo,
-                CreatedBy = actor,
-                CreatedAt = now
-            };
-            await _payments.AddAsync(entity, token);
-
-            grn.PaidAmount += request.Amount;
-            grn.BalanceAmount -= request.Amount;
-
-            return entity;
-        }, ct);
-
-        return Map(payment);
-    }
-
-    public async Task<IReadOnlyList<GrnPaymentDto>> ListAsync(int grnId, CancellationToken ct = default)
-    {
-        if (!await _grns.Query().AnyAsync(g => g.GrnId == grnId, ct))
-            throw new NotFoundException($"GRN {grnId} was not found.");
-
-        return await _payments.Query().AsNoTracking()
-            .Where(p => p.GrnId == grnId)
-            .OrderByDescending(p => p.GrnPaymentId)
-            .Select(p => new GrnPaymentDto(
-                p.GrnPaymentId, p.GrnId, p.Amount, p.PaymentDate,
-                p.GlBankAccountId, p.BankAccountName, p.Reference, p.GlJournalNo, p.CreatedAt))
-            .ToListAsync(ct);
-    }
-
-    private static GrnPaymentDto Map(GrnPayment p) => new(
-        p.GrnPaymentId, p.GrnId, p.Amount, p.PaymentDate,
-        p.GlBankAccountId, p.BankAccountName, p.Reference, p.GlJournalNo, p.CreatedAt);
-}

Backend/ERPCore/Services/GrnService.cs

@@ -92,7 +92,8 @@ public sealed class GrnService : IGrnService
             .Skip(query.Skip).Take(query.PageSize)
             .Select(g => new GrnSummaryDto(
                 g.GrnId, g.DocNo, g.PoId, g.VendorId, g.WarehouseId, g.Status,
-                g.CreatedBy, g.CreatedAt, g.PostedAt, g.Lines.Count, g.PaidAmount, g.BalanceAmount))
+                g.CreatedBy, g.CreatedAt, g.PostedAt, g.Lines.Count,
+                g.PurchaseInvoiceId, g.PurchaseInvoice != null ? g.PurchaseInvoice.DocNo : null))
             .ToListAsync(ct);
 
         return PagedResponse<GrnSummaryDto>.Create(rows, query.Page, query.PageSize, total);
@@ -102,6 +103,7 @@ public sealed class GrnService : IGrnService
     {
         var grn = await _grns.Query().AsNoTracking()
             .Include(g => g.Lines).ThenInclude(l => l.WarrantyNumbers)
+            .Include(g => g.PurchaseInvoice)
             .FirstOrDefaultAsync(g => g.GrnId == grnId, ct);
         return grn is null ? null : Map(grn);
     }
@@ -302,15 +304,13 @@ public sealed class GrnService : IGrnService
             grn.PostedAt = now;
             grn.GlJournalNo = posted.JournalNo;
             grn.GlPostedAt = now;
-            grn.PaidAmount = 0m;
-            grn.BalanceAmount = totalPayable;
 
             await UpdatePoStatusAsync(grn.PoId, token);
             return 0;
         }, ct);
 
         return new GrnConfirmResultDto(
-            grn.GrnId, grn.Status, now, grn.GlJournalNo ?? string.Empty, grn.BalanceAmount,
+            grn.GrnId, grn.Status, now, grn.GlJournalNo ?? string.Empty,
             createdLayers.Select(ToCreatedLayer).ToList(),
             ledgerRefs.Select(l => l.LedgerId).ToList(),
             await GetPoStatusAsync(grn.PoId, ct));
@@ -437,7 +437,7 @@ public sealed class GrnService : IGrnService
             .Select(l => l.LedgerId).ToListAsync(ct);
 
         return new GrnConfirmResultDto(
-            grn.GrnId, grn.Status, grn.PostedAt ?? grn.CreatedAt, grn.GlJournalNo ?? string.Empty, grn.BalanceAmount,
+            grn.GrnId, grn.Status, grn.PostedAt ?? grn.CreatedAt, grn.GlJournalNo ?? string.Empty,
             layers.Select(ToCreatedLayer).ToList(), ledgerRefs, await GetPoStatusAsync(grn.PoId, ct));
     }
 
@@ -446,7 +446,7 @@ public sealed class GrnService : IGrnService
 
     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.GlJournalNo, g.PaidAmount, g.BalanceAmount,
+        g.GlJournalNo, g.PurchaseInvoiceId, g.PurchaseInvoice?.DocNo,
         g.Lines.OrderBy(l => l.GrnLineId).Select(l => new GrnLineDto(
             l.GrnLineId, l.PoLineId, l.ItemId, l.BinId, l.Qty, l.UnitCost, l.PoUnitPrice,
             l.DiscountPct, l.NetUnitCost, l.VatPct, l.VatAmount, l.ReceivedValue, l.LineTotal,

Backend/ERPCore/Services/Interfaces/IGrnPaymentService.cs

@@ -1,10 +0,0 @@
-using ERPCore.Dtos.Grn;
-
-namespace ERPCore.Services.Interfaces;
-
-/// <summary>Vendor payments against a confirmed GRN's balance (installments allowed).</summary>
-public interface IGrnPaymentService
-{
-    Task<GrnPaymentDto> PayAsync(int grnId, CreateGrnPaymentRequest request, CancellationToken ct = default);
-    Task<IReadOnlyList<GrnPaymentDto>> ListAsync(int grnId, CancellationToken ct = default);
-}

Backend/ERPCore/Services/Interfaces/IPurchaseInvoicePaymentService.cs

@@ -0,0 +1,10 @@
+using ERPCore.Dtos.Procurement;
+
+namespace ERPCore.Services.Interfaces;
+
+/// <summary>Vendor payments against a Posted purchase invoice's balance (installments allowed).</summary>
+public interface IPurchaseInvoicePaymentService
+{
+    Task<PurchaseInvoicePaymentDto> PayAsync(int purchaseInvoiceId, CreatePurchaseInvoicePaymentRequest request, CancellationToken ct = default);
+    Task<IReadOnlyList<PurchaseInvoicePaymentDto>> ListAsync(int purchaseInvoiceId, CancellationToken ct = default);
+}

Backend/ERPCore/Services/Interfaces/IPurchaseInvoiceService.cs

@@ -0,0 +1,20 @@
+using ERPCore.Common.Http;
+using ERPCore.Domain.Enums;
+using ERPCore.Dtos.Common;
+using ERPCore.Dtos.Grn;
+using ERPCore.Dtos.Procurement;
+
+namespace ERPCore.Services.Interfaces;
+
+public interface IPurchaseInvoiceService
+{
+    Task<PagedResponse<PurchaseInvoiceSummaryDto>> ListAsync(PageQuery query, PurchaseInvoiceStatus? status, int? vendorId, CancellationToken ct = default);
+    Task<ETagged<PurchaseInvoiceDto>?> GetAsync(int purchaseInvoiceId, CancellationToken ct = default);
+    Task<ETagged<PurchaseInvoiceDto>> CreateAsync(CreatePurchaseInvoiceRequest request, CancellationToken ct = default);
+    Task<ETagged<PurchaseInvoiceDto>> UpdateAsync(int purchaseInvoiceId, UpdatePurchaseInvoiceRequest request, uint expectedRowVersion, CancellationToken ct = default);
+    Task<PurchaseInvoiceDto> PostAsync(int purchaseInvoiceId, CancellationToken ct = default);
+    Task<PurchaseInvoiceDto> CancelAsync(int purchaseInvoiceId, CancellationToken ct = default);
+
+    /// <summary>Confirmed, not-yet-invoiced GRNs for a vendor — candidates for a new/edited invoice.</summary>
+    Task<IReadOnlyList<GrnEligibleForInvoiceDto>> ListEligibleGrnsAsync(int vendorId, CancellationToken ct = default);
+}

Backend/ERPCore/Services/PurchaseInvoicePaymentService.cs

@@ -0,0 +1,119 @@
+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.Gl;
+using ERPCore.Services.Interfaces;
+using ERPCore.System.Errors;
+using Microsoft.EntityFrameworkCore;
+
+namespace ERPCore.Services;
+
+/// <summary>
+/// Vendor payments against a Posted purchase invoice. Multiple installments are allowed
+/// until <see cref="PurchaseInvoice.BalanceAmount"/> reaches zero. Each payment posts its
+/// own real GL journal entry (Debit Accounts Payable / Credit the selected bank-or-cash
+/// account) — the mirror image of <see cref="SalesInvoicePaymentService"/> (that one
+/// credits Accounts Receivable when the customer pays; this one debits Accounts Payable
+/// when the vendor is paid) — using the same call-GL-before-commit pattern so a
+/// rejected/unreachable GL post rolls back the whole payment atomically.
+/// </summary>
+public sealed class PurchaseInvoicePaymentService : IPurchaseInvoicePaymentService
+{
+    private readonly IRepository<PurchaseInvoice> _invoices;
+    private readonly IRepository<PurchaseInvoicePayment> _payments;
+    private readonly IGeneralLedgerService _gl;
+    private readonly ICurrentUser _currentUser;
+    private readonly IUnitOfWork _uow;
+    private readonly string _glAccountsPayableCode;
+
+    public PurchaseInvoicePaymentService(
+        IRepository<PurchaseInvoice> invoices, IRepository<PurchaseInvoicePayment> payments, IGeneralLedgerService gl,
+        ICurrentUser currentUser, IUnitOfWork uow, IConfiguration configuration)
+    {
+        _invoices = invoices;
+        _payments = payments;
+        _gl = gl;
+        _currentUser = currentUser;
+        _uow = uow;
+        _glAccountsPayableCode = configuration["PurchaseInvoice:GlAccountsPayableCode"] ?? string.Empty;
+    }
+
+    public async Task<PurchaseInvoicePaymentDto> PayAsync(int purchaseInvoiceId, CreatePurchaseInvoicePaymentRequest request, CancellationToken ct = default)
+    {
+        var invoice = await _invoices.Query().FirstOrDefaultAsync(i => i.PurchaseInvoiceId == purchaseInvoiceId, ct)
+            ?? throw new NotFoundException($"Purchase invoice {purchaseInvoiceId} was not found.");
+
+        if (invoice.Status != PurchaseInvoiceStatus.Posted)
+            throw new DomainException(ErrorCodes.PurchaseInvoiceNotPayable, $"Purchase invoice {purchaseInvoiceId} must be posted before it can be paid.", 409);
+        if (request.Amount > invoice.BalanceAmount)
+            throw new DomainException(ErrorCodes.PurchaseInvoicePaymentExceedsBalance,
+                $"Payment amount {request.Amount} exceeds the remaining balance {invoice.BalanceAmount}.", 400);
+
+        var accounts = await _gl.ListBankAccountsAsync(ct);
+        var account = accounts.FirstOrDefault(a => a.AccountId == request.GlBankAccountId)
+            ?? throw new DomainException(ErrorCodes.PurchaseInvoiceBankAccountNotFound, $"Bank/cash account {request.GlBankAccountId} was not found.", 404);
+
+        var actor = _currentUser.AuditUserId;
+        var now = DateTime.UtcNow;
+
+        var payment = await _uow.ExecuteInTransactionAsync(async token =>
+        {
+            var period = await _gl.GetPeriodByDateAsync(DateOnly.FromDateTime(now), token);
+            var posted = await _gl.PostJournalEntryAsync(new GlJournalEntryRequest
+            {
+                PeriodId = period.PeriodId,
+                EntryDate = DateOnly.FromDateTime(now),
+                SourceModule = "PURCHASE_INVOICE_PAYMENT",
+                Reference = invoice.DocNo,
+                Narration = $"Payment against invoice {invoice.DocNo}",
+                Lines =
+                [
+                    new GlJournalEntryLineRequest(_glAccountsPayableCode, request.Amount, 0m, $"Payment against invoice {invoice.DocNo}"),
+                    new GlJournalEntryLineRequest(account.GlAccountCode, 0m, request.Amount, $"Payment against invoice {invoice.DocNo}")
+                ]
+            }, token);
+
+            var entity = new PurchaseInvoicePayment
+            {
+                PurchaseInvoiceId = invoice.PurchaseInvoiceId,
+                Amount = request.Amount,
+                PaymentDate = now,
+                GlBankAccountId = account.AccountId,
+                BankAccountName = account.AccountName,
+                Reference = request.Reference,
+                GlJournalNo = posted.JournalNo,
+                CreatedBy = actor,
+                CreatedAt = now
+            };
+            await _payments.AddAsync(entity, token);
+
+            invoice.PaidAmount += request.Amount;
+            invoice.BalanceAmount -= request.Amount;
+
+            return entity;
+        }, ct);
+
+        return Map(payment);
+    }
+
+    public async Task<IReadOnlyList<PurchaseInvoicePaymentDto>> ListAsync(int purchaseInvoiceId, CancellationToken ct = default)
+    {
+        if (!await _invoices.Query().AnyAsync(i => i.PurchaseInvoiceId == purchaseInvoiceId, ct))
+            throw new NotFoundException($"Purchase invoice {purchaseInvoiceId} was not found.");
+
+        return await _payments.Query().AsNoTracking()
+            .Where(p => p.PurchaseInvoiceId == purchaseInvoiceId)
+            .OrderByDescending(p => p.PurchaseInvoicePaymentId)
+            .Select(p => new PurchaseInvoicePaymentDto(
+                p.PurchaseInvoicePaymentId, p.PurchaseInvoiceId, p.Amount, p.PaymentDate,
+                p.GlBankAccountId, p.BankAccountName, p.Reference, p.GlJournalNo, p.CreatedAt))
+            .ToListAsync(ct);
+    }
+
+    private static PurchaseInvoicePaymentDto Map(PurchaseInvoicePayment p) => new(
+        p.PurchaseInvoicePaymentId, p.PurchaseInvoiceId, p.Amount, p.PaymentDate,
+        p.GlBankAccountId, p.BankAccountName, p.Reference, p.GlJournalNo, p.CreatedAt);
+}

Backend/ERPCore/Services/PurchaseInvoiceService.cs

@@ -0,0 +1,303 @@
+using ERPCore.Common.Http;
+using ERPCore.Domain;
+using ERPCore.Domain.Entities;
+using ERPCore.Domain.Enums;
+using ERPCore.Dtos.Common;
+using ERPCore.Dtos.Grn;
+using ERPCore.Dtos.Procurement;
+using ERPCore.Infra.Auth;
+using ERPCore.Infra.UoW;
+using ERPCore.Repositories.Interfaces;
+using ERPCore.Services.Gl;
+using ERPCore.Services.Interfaces;
+using ERPCore.System.Errors;
+using Microsoft.EntityFrameworkCore;
+
+namespace ERPCore.Services;
+
+/// <summary>
+/// Purchase invoice service. A purchase invoice consolidates one or more Confirmed
+/// GRNs for the same vendor into a single vendor-facing document — each linked GRN
+/// becomes one <see cref="PurchaseInvoiceLine"/>, a straight sum of that GRN's line
+/// totals (no re-itemization). Draft invoices are fully editable (GRNs can be
+/// re-selected); Post reclassifies the GRN clearing balance to Accounts Payable via a
+/// real GL journal entry (mirrors <see cref="SalesInvoiceService"/>'s AR recognition);
+/// vendor payments are then recorded against this aggregate (see
+/// <see cref="PurchaseInvoicePaymentService"/>) rather than per-GRN.
+/// </summary>
+public sealed class PurchaseInvoiceService : IPurchaseInvoiceService
+{
+    private readonly IRepository<PurchaseInvoice> _invoices;
+    private readonly IRepository<Vendor> _vendors;
+    private readonly IRepository<Grn> _grns;
+    private readonly ICurrentUser _currentUser;
+    private readonly INumberSequenceService _numbers;
+    private readonly IUnitOfWork _uow;
+    private readonly IGeneralLedgerService _gl;
+    private readonly string _glClearingAccountCode;
+    private readonly string _glAccountsPayableCode;
+
+    public PurchaseInvoiceService(
+        IRepository<PurchaseInvoice> invoices, IRepository<Vendor> vendors, IRepository<Grn> grns,
+        ICurrentUser currentUser, INumberSequenceService numbers, IUnitOfWork uow,
+        IGeneralLedgerService gl, IConfiguration configuration)
+    {
+        _invoices = invoices;
+        _vendors = vendors;
+        _grns = grns;
+        _currentUser = currentUser;
+        _numbers = numbers;
+        _uow = uow;
+        _gl = gl;
+        _glClearingAccountCode = configuration["PurchaseInvoice:GlClearingAccountCode"] ?? string.Empty;
+        _glAccountsPayableCode = configuration["PurchaseInvoice:GlAccountsPayableCode"] ?? string.Empty;
+    }
+
+    public async Task<PagedResponse<PurchaseInvoiceSummaryDto>> ListAsync(PageQuery query, PurchaseInvoiceStatus? status, int? vendorId, CancellationToken ct = default)
+    {
+        IQueryable<PurchaseInvoice> q = _invoices.Query().AsNoTracking().Include(x => x.Lines);
+        if (!string.IsNullOrWhiteSpace(query.Q))
+        {
+            var term = query.Q.Trim();
+            q = q.Where(x => EF.Functions.ILike(x.DocNo, $"%{term}%")
+                || EF.Functions.ILike(x.VendorInvoiceNo, $"%{term}%")
+                || EF.Functions.ILike(x.VendorSnapshotName, $"%{term}%"));
+        }
+        if (status is not null) q = q.Where(x => x.Status == status);
+        if (vendorId is not null) q = q.Where(x => x.VendorId == vendorId);
+
+        var total = await q.CountAsync(ct);
+        var rows = await q.OrderByDescending(x => x.PurchaseInvoiceId).Skip(query.Skip).Take(query.PageSize).ToListAsync(ct);
+
+        return PagedResponse<PurchaseInvoiceSummaryDto>.Create(rows.Select(MapSummary).ToList(), query.Page, query.PageSize, total);
+    }
+
+    public async Task<ETagged<PurchaseInvoiceDto>?> GetAsync(int purchaseInvoiceId, CancellationToken ct = default)
+    {
+        var invoice = await _invoices.Query().AsNoTracking()
+            .Include(x => x.Lines).ThenInclude(l => l.Grn)
+            .FirstOrDefaultAsync(x => x.PurchaseInvoiceId == purchaseInvoiceId, ct);
+        return invoice is null ? null : new ETagged<PurchaseInvoiceDto>(MapInvoice(invoice), invoice.RowVersion);
+    }
+
+    public async Task<ETagged<PurchaseInvoiceDto>> CreateAsync(CreatePurchaseInvoiceRequest request, CancellationToken ct = default)
+    {
+        var vendor = await _vendors.Query().AsNoTracking().FirstOrDefaultAsync(v => v.VendorId == request.VendorId, ct)
+            ?? throw new DomainException(ErrorCodes.Validation, $"Vendor {request.VendorId} does not exist.", 422);
+
+        var vendorInvoiceNo = request.VendorInvoiceNo.Trim();
+        await EnsureVendorInvoiceNoIsUniqueAsync(request.VendorId, vendorInvoiceNo, excludingPurchaseInvoiceId: null, ct);
+
+        var grns = await LoadAndValidateGrnsAsync(request.VendorId, request.GrnIds, excludingPurchaseInvoiceId: null, ct);
+
+        var invoice = await _uow.ExecuteInTransactionAsync(async token =>
+        {
+            var entity = new PurchaseInvoice
+            {
+                DocNo = await _numbers.NextAsync(DocumentTypes.PurchaseInvoice, token),
+                VendorInvoiceNo = vendorInvoiceNo,
+                VendorInvoiceDate = request.VendorInvoiceDate,
+                VendorId = request.VendorId,
+                VendorSnapshotName = vendor.Name,
+                VendorSnapshotTaxNo = vendor.TaxReg,
+                Status = PurchaseInvoiceStatus.Draft,
+                CreatedBy = _currentUser.AuditUserId,
+                CreatedAt = DateTime.UtcNow,
+                Lines = grns.Select(BuildLine).ToList()
+            };
+            Recalculate(entity);
+            await _invoices.AddAsync(entity, token);
+
+            foreach (var grn in grns) grn.PurchaseInvoice = entity;
+
+            return entity;
+        }, ct);
+
+        return new ETagged<PurchaseInvoiceDto>(MapInvoice(invoice), invoice.RowVersion);
+    }
+
+    public async Task<ETagged<PurchaseInvoiceDto>> UpdateAsync(int purchaseInvoiceId, UpdatePurchaseInvoiceRequest request, uint expectedRowVersion, CancellationToken ct = default)
+    {
+        var invoice = await _invoices.Query()
+            .Include(x => x.Lines).ThenInclude(l => l.Grn)
+            .FirstOrDefaultAsync(x => x.PurchaseInvoiceId == purchaseInvoiceId, ct)
+            ?? throw new NotFoundException($"Purchase invoice {purchaseInvoiceId} was not found.");
+
+        if (invoice.RowVersion != expectedRowVersion)
+            throw new DomainException(ErrorCodes.ConcurrencyConflict, "The purchase invoice was modified by another request.", 412);
+        if (invoice.Status != PurchaseInvoiceStatus.Draft)
+            throw new DomainException(ErrorCodes.PurchaseInvoiceNotEditable, $"Purchase invoice {purchaseInvoiceId} is {invoice.Status} and cannot be edited.", 409);
+
+        var vendor = await _vendors.Query().AsNoTracking().FirstOrDefaultAsync(v => v.VendorId == request.VendorId, ct)
+            ?? throw new DomainException(ErrorCodes.Validation, $"Vendor {request.VendorId} does not exist.", 422);
+
+        var vendorInvoiceNo = request.VendorInvoiceNo.Trim();
+        await EnsureVendorInvoiceNoIsUniqueAsync(request.VendorId, vendorInvoiceNo, excludingPurchaseInvoiceId: purchaseInvoiceId, ct);
+
+        var grns = await LoadAndValidateGrnsAsync(request.VendorId, request.GrnIds, excludingPurchaseInvoiceId: purchaseInvoiceId, ct);
+
+        // Free GRNs that were linked to this invoice but are no longer selected.
+        var newGrnIds = grns.Select(g => g.GrnId).ToHashSet();
+        foreach (var line in invoice.Lines)
+            if (line.Grn is not null && !newGrnIds.Contains(line.Grn.GrnId)) line.Grn.PurchaseInvoiceId = null;
+
+        invoice.VendorId = request.VendorId;
+        invoice.VendorInvoiceNo = vendorInvoiceNo;
+        invoice.VendorInvoiceDate = request.VendorInvoiceDate;
+        invoice.VendorSnapshotName = vendor.Name;
+        invoice.VendorSnapshotTaxNo = vendor.TaxReg;
+        invoice.Lines.Clear();
+        foreach (var line in grns.Select(BuildLine)) invoice.Lines.Add(line);
+        foreach (var grn in grns) grn.PurchaseInvoice = invoice;
+        Recalculate(invoice);
+        invoice.UpdatedAt = DateTime.UtcNow;
+
+        await _uow.SaveChangesAsync(ct);
+        return new ETagged<PurchaseInvoiceDto>(MapInvoice(invoice), invoice.RowVersion);
+    }
+
+    public async Task<PurchaseInvoiceDto> PostAsync(int purchaseInvoiceId, CancellationToken ct = default)
+    {
+        var invoice = await _invoices.Query()
+            .Include(x => x.Lines).ThenInclude(l => l.Grn)
+            .FirstOrDefaultAsync(x => x.PurchaseInvoiceId == purchaseInvoiceId, ct)
+            ?? throw new NotFoundException($"Purchase invoice {purchaseInvoiceId} was not found.");
+
+        if (invoice.Status != PurchaseInvoiceStatus.Draft)
+            throw new ConflictException($"Purchase invoice {purchaseInvoiceId} is {invoice.Status} and cannot be posted.");
+
+        var now = DateTime.UtcNow;
+
+        await _uow.ExecuteInTransactionAsync(async token =>
+        {
+            // Reclassify the GRN clearing balance to Accounts Payable — the mirror image of
+            // SalesInvoicePaymentService's AR credit — before committing, so a GL rejection
+            // rolls the whole post back (same atomicity approach as GrnService.ConfirmAsync).
+            var period = await _gl.GetPeriodByDateAsync(DateOnly.FromDateTime(now), token);
+            var posted = await _gl.PostJournalEntryAsync(new GlJournalEntryRequest
+            {
+                PeriodId = period.PeriodId,
+                EntryDate = DateOnly.FromDateTime(now),
+                SourceModule = "PURCHASE_INVOICE",
+                Reference = invoice.DocNo,
+                Narration = $"Vendor invoice recognized - {invoice.DocNo}",
+                Lines =
+                [
+                    new GlJournalEntryLineRequest(_glClearingAccountCode, invoice.GrandTotal, 0m, $"Purchase invoice {invoice.DocNo}"),
+                    new GlJournalEntryLineRequest(_glAccountsPayableCode, 0m, invoice.GrandTotal, $"Purchase invoice {invoice.DocNo}")
+                ]
+            }, token);
+
+            invoice.Status = PurchaseInvoiceStatus.Posted;
+            invoice.GlJournalNo = posted.JournalNo;
+            invoice.GlPostedAt = now;
+            invoice.UpdatedAt = now;
+            return 0;
+        }, ct);
+
+        return MapInvoice(invoice);
+    }
+
+    public async Task<PurchaseInvoiceDto> CancelAsync(int purchaseInvoiceId, CancellationToken ct = default)
+    {
+        var invoice = await _invoices.Query()
+            .Include(x => x.Lines).ThenInclude(l => l.Grn)
+            .FirstOrDefaultAsync(x => x.PurchaseInvoiceId == purchaseInvoiceId, ct)
+            ?? throw new NotFoundException($"Purchase invoice {purchaseInvoiceId} was not found.");
+
+        if (invoice.Status != PurchaseInvoiceStatus.Draft)
+            throw new ConflictException($"Purchase invoice {purchaseInvoiceId} is {invoice.Status} and cannot be cancelled.");
+
+        var dto = MapInvoice(invoice);
+
+        // Cancelling frees the consolidated GRNs so they can be picked up by a later invoice —
+        // the link rows are removed (the unique index on GrnId only tracks the active link),
+        // while the Cancelled header row itself remains for audit history.
+        foreach (var line in invoice.Lines)
+            if (line.Grn is not null) line.Grn.PurchaseInvoiceId = null;
+        invoice.Lines.Clear();
+        invoice.Status = PurchaseInvoiceStatus.Cancelled;
+        invoice.UpdatedAt = DateTime.UtcNow;
+        await _uow.SaveChangesAsync(ct);
+
+        return dto with { Status = PurchaseInvoiceStatus.Cancelled, UpdatedAt = invoice.UpdatedAt };
+    }
+
+    public async Task<IReadOnlyList<GrnEligibleForInvoiceDto>> ListEligibleGrnsAsync(int vendorId, CancellationToken ct = default)
+    {
+        return await _grns.Query().AsNoTracking()
+            .Where(g => g.VendorId == vendorId && g.Status == GrnStatus.Confirmed && g.PurchaseInvoiceId == null)
+            .OrderBy(g => g.PostedAt)
+            .Select(g => new GrnEligibleForInvoiceDto(
+                g.GrnId, g.DocNo, g.PostedAt ?? g.CreatedAt, g.WarehouseId, g.Lines.Count,
+                g.Lines.Sum(l => l.ReceivedValue), g.Lines.Sum(l => l.VatAmount), g.Lines.Sum(l => l.LineTotal)))
+            .ToListAsync(ct);
+    }
+
+    private async Task EnsureVendorInvoiceNoIsUniqueAsync(int vendorId, string vendorInvoiceNo, int? excludingPurchaseInvoiceId, CancellationToken ct)
+    {
+        var duplicate = await _invoices.Query().AsNoTracking().AnyAsync(x =>
+            x.VendorId == vendorId
+            && x.Status != PurchaseInvoiceStatus.Cancelled
+            && x.VendorInvoiceNo == vendorInvoiceNo
+            && (excludingPurchaseInvoiceId == null || x.PurchaseInvoiceId != excludingPurchaseInvoiceId), ct);
+        if (duplicate)
+            throw new DomainException(ErrorCodes.DuplicateVendorInvoiceNo,
+                $"Vendor invoice number '{vendorInvoiceNo}' already exists for this vendor.", 409);
+    }
+
+    private async Task<List<Grn>> LoadAndValidateGrnsAsync(int vendorId, List<int> grnIds, int? excludingPurchaseInvoiceId, CancellationToken ct)
+    {
+        var distinctIds = grnIds.Distinct().ToList();
+        var grns = await _grns.Query().Include(g => g.Lines)
+            .Where(g => distinctIds.Contains(g.GrnId)).ToListAsync(ct);
+
+        if (grns.Count != distinctIds.Count)
+            throw new DomainException(ErrorCodes.Validation, "One or more selected GRNs do not exist.", 422);
+
+        foreach (var grn in grns)
+        {
+            if (grn.Status != GrnStatus.Confirmed)
+                throw new DomainException(ErrorCodes.GrnNotConfirmed, $"GRN {grn.DocNo} must be confirmed before it can be invoiced.", 409);
+            if (grn.VendorId != vendorId)
+                throw new DomainException(ErrorCodes.GrnVendorMismatch, $"GRN {grn.DocNo} belongs to a different vendor.", 409);
+            if (grn.PurchaseInvoiceId is not null && grn.PurchaseInvoiceId != excludingPurchaseInvoiceId)
+                throw new DomainException(ErrorCodes.GrnAlreadyInvoiced, $"GRN {grn.DocNo} is already linked to another purchase invoice.", 409);
+        }
+
+        return grns;
+    }
+
+    private static PurchaseInvoiceLine BuildLine(Grn grn) => new()
+    {
+        Grn = grn,
+        GrnId = grn.GrnId,
+        Subtotal = grn.Lines.Sum(l => l.ReceivedValue),
+        VatTotal = grn.Lines.Sum(l => l.VatAmount),
+        LineTotal = grn.Lines.Sum(l => l.LineTotal)
+    };
+
+    private static void Recalculate(PurchaseInvoice invoice)
+    {
+        invoice.Subtotal = invoice.Lines.Sum(x => x.Subtotal);
+        invoice.VatTotal = invoice.Lines.Sum(x => x.VatTotal);
+        invoice.GrandTotal = invoice.Lines.Sum(x => x.LineTotal);
+        invoice.PaidAmount = 0m;
+        invoice.BalanceAmount = invoice.GrandTotal;
+    }
+
+    private static PurchaseInvoiceTotalsDto MapTotals(PurchaseInvoice x) => new(
+        x.Subtotal, x.VatTotal, x.GrandTotal, x.PaidAmount, x.BalanceAmount);
+
+    private static PurchaseInvoiceSummaryDto MapSummary(PurchaseInvoice x) => new(
+        x.PurchaseInvoiceId, x.DocNo, x.VendorInvoiceNo, x.VendorInvoiceDate, x.VendorId,
+        x.VendorSnapshotName, x.Status, x.Lines.Count, MapTotals(x), x.CreatedAt, x.GlJournalNo);
+
+    private static PurchaseInvoiceDto MapInvoice(PurchaseInvoice x) => new(
+        x.PurchaseInvoiceId, x.DocNo, x.VendorInvoiceNo, x.VendorInvoiceDate, x.VendorId,
+        x.VendorSnapshotName, x.VendorSnapshotTaxNo, x.Status, x.Lines.Count, x.CreatedBy, x.CreatedAt, x.UpdatedAt,
+        x.GlJournalNo, x.GlPostedAt, MapTotals(x),
+        x.Lines.OrderBy(l => l.PurchaseInvoiceLineId).Select(l => new PurchaseInvoiceLineDto(
+            l.PurchaseInvoiceLineId, l.GrnId, l.Grn?.DocNo ?? string.Empty, l.Grn?.PostedAt ?? default,
+            l.Subtotal, l.VatTotal, l.LineTotal)).ToList());
+}

Backend/ERPCore/Services/SalesInvoicePaymentService.cs

@@ -16,8 +16,8 @@ namespace ERPCore.Services;
 /// until <see cref="SalesInvoice.BalanceAmount"/> reaches zero. Each payment posts its
 /// own real GL journal entry (Debit the selected bank-or-cash account / Credit Accounts
 /// Receivable) before being recorded, using the same call-GL-before-commit pattern as
-/// <see cref="GrnPaymentService"/> — the mirror image of it (that one credits a payable
-/// clearing account when vendor-paid; this one credits the receivable asset when
+/// <see cref="PurchaseInvoicePaymentService"/> — the mirror image of it (that one debits a
+/// payable account when the vendor is paid; this one credits the receivable asset when
 /// customer-paid) — so a rejected/unreachable GL post rolls back the whole payment atomically.
 /// </summary>
 public sealed class SalesInvoicePaymentService : ISalesInvoicePaymentService

Backend/ERPCore/System/Errors/ErrorCodes.cs

@@ -73,13 +73,18 @@ public static class ErrorCodes
     // General Ledger typed internal calls (GRN receipt/payment posting, docs/12 §5's deferred work)
     public const string GlRequestFailed = "GL_REQUEST_FAILED";
 
-    // GRN payments
-    public const string GrnNotPayable = "GRN_NOT_PAYABLE";
-    public const string GrnPaymentExceedsBalance = "GRN_PAYMENT_EXCEEDS_BALANCE";
-    public const string GrnBankAccountNotFound = "GRN_BANK_ACCOUNT_NOT_FOUND";
-
     // Sales invoice payments
     public const string SalesInvoiceNotPayable = "SALES_INVOICE_NOT_PAYABLE";
     public const string SalesInvoicePaymentExceedsBalance = "SALES_INVOICE_PAYMENT_EXCEEDS_BALANCE";
     public const string SalesInvoiceBankAccountNotFound = "SALES_INVOICE_BANK_ACCOUNT_NOT_FOUND";
+
+    // Purchase invoices (consolidate Confirmed GRNs; vendor payments now tracked here, not on the GRN)
+    public const string GrnAlreadyInvoiced = "GRN_ALREADY_INVOICED";
+    public const string GrnVendorMismatch = "GRN_VENDOR_MISMATCH";
+    public const string GrnNotConfirmed = "GRN_NOT_CONFIRMED";
+    public const string PurchaseInvoiceNotEditable = "PURCHASE_INVOICE_NOT_EDITABLE";
+    public const string DuplicateVendorInvoiceNo = "DUPLICATE_VENDOR_INVOICE_NO";
+    public const string PurchaseInvoiceNotPayable = "PURCHASE_INVOICE_NOT_PAYABLE";
+    public const string PurchaseInvoicePaymentExceedsBalance = "PURCHASE_INVOICE_PAYMENT_EXCEEDS_BALANCE";
+    public const string PurchaseInvoiceBankAccountNotFound = "PURCHASE_INVOICE_BANK_ACCOUNT_NOT_FOUND";
 }

Backend/ERPCore/appsettings.json

@@ -47,5 +47,9 @@
   "SalesInvoice": {
     "GlAccountsReceivableCode": "1300"
   },
+  "PurchaseInvoice": {
+    "GlClearingAccountCode": "2000",
+    "GlAccountsPayableCode": "2200"
+  },
   "AllowedHosts": "*"
 }