diff --git a/API/ROLAC.API.Tests/Services/ExpenseServiceTests.cs b/API/ROLAC.API.Tests/Services/ExpenseServiceTests.cs
new file mode 100644
index 0000000..0a985e3
--- /dev/null
+++ b/API/ROLAC.API.Tests/Services/ExpenseServiceTests.cs
@@ -0,0 +1,155 @@
+using Microsoft.EntityFrameworkCore;
+using System.Security.Claims;
+using System.Text;
+using Microsoft.AspNetCore.Http;
+using Moq;
+using ROLAC.API.Data;
+using ROLAC.API.Data.Interceptors;
+using ROLAC.API.DTOs.Expense;
+using ROLAC.API.Entities;
+using ROLAC.API.Services;
+using ROLAC.API.Services.Storage;
+using Xunit;
+
+namespace ROLAC.API.Tests.Services;
+
+public class ExpenseServiceTests
+{
+    private sealed class FakeStorage : IFileStorage
+    {
+        public Dictionary<string, byte[]> Files = new();
+        public Task<string> SaveAsync(Stream c, string p, CancellationToken ct = default)
+        { using var ms = new MemoryStream(); c.CopyTo(ms); Files[p] = ms.ToArray(); return Task.FromResult(p); }
+        public Task<Stream?> OpenReadAsync(string p, CancellationToken ct = default)
+        => Task.FromResult<Stream?>(Files.TryGetValue(p, out var b) ? new MemoryStream(b) : null);
+        public Task DeleteAsync(string p, CancellationToken ct = default) { Files.Remove(p); return Task.CompletedTask; }
+    }
+
+    private static AppDbContext BuildDb(string userId)
+    {
+        var claims = new[] { new Claim(ClaimTypes.NameIdentifier, userId) };
+        var ctx    = new DefaultHttpContext { User = new(new ClaimsIdentity(claims)) };
+        var mock   = new Mock<IHttpContextAccessor>();
+        mock.Setup(x => x.HttpContext).Returns(ctx);
+        return new AppDbContext(new DbContextOptionsBuilder<AppDbContext>()
+            .UseInMemoryDatabase(Guid.NewGuid().ToString())
+            .AddInterceptors(new AuditSaveChangesInterceptor(mock.Object)).Options);
+    }
+
+    private static (ExpenseService svc, AppDbContext db, FakeStorage fs) Build(string userId = "u1")
+    {
+        var db = BuildDb(userId);
+        db.Ministries.Add(new Ministry { Id = 1, Name_en = "Worship" });
+        db.ExpenseCategoryGroups.Add(new ExpenseCategoryGroup { Id = 1, Name_en = "Equipment" });
+        db.ExpenseSubCategories.Add(new ExpenseSubCategory { Id = 1, GroupId = 1, Name_en = "Purchase" });
+        db.SaveChanges();
+        var fs = new FakeStorage();
+        return (SvcAs(db, fs, userId), db, fs);
+    }
+
+    private static ExpenseService SvcAs(AppDbContext db, FakeStorage fs, string userId)
+    {
+        var http = new Mock<IHttpContextAccessor>();
+        var ctx  = new DefaultHttpContext { User = new(new ClaimsIdentity(new[] { new Claim(ClaimTypes.NameIdentifier, userId) })) };
+        http.Setup(x => x.HttpContext).Returns(ctx);
+        return new ExpenseService(db, http.Object, fs);
+    }
+
+    private static CreateExpenseRequest Reimb() => new()
+    {
+        Type = "StaffReimbursement", MinistryId = 1, CategoryGroupId = 1, SubCategoryId = 1,
+        Amount = 45.50m, Description = "Batteries", ExpenseDate = new DateOnly(2026, 5, 28),
+    };
+
+    private static UpdateExpenseRequest CloneToUpdate(CreateExpenseRequest r) => new()
+    {
+        Type = r.Type, MinistryId = r.MinistryId, CategoryGroupId = r.CategoryGroupId,
+        SubCategoryId = r.SubCategoryId, Amount = r.Amount, Description = r.Description,
+        VendorName = r.VendorName, MemberId = r.MemberId, CheckNumber = r.CheckNumber,
+        ExpenseDate = r.ExpenseDate, Notes = r.Notes,
+    };
+
+    [Fact]
+    public async Task Create_Vendor_AsFinance_IsImmediatelyPaid()
+    {
+        var (svc, db, _) = Build();
+        var r = Reimb(); r.Type = "VendorPayment"; r.VendorName = "ABC"; r.CheckNumber = "2051";
+        var id = await svc.CreateAsync(r, isFinance: true);
+        Assert.Equal("Paid", (await db.Expenses.FindAsync(id))!.Status);
+    }
+
+    [Fact]
+    public async Task Create_Reimbursement_IsDraft_WithSubmitter()
+    {
+        var (svc, db, _) = Build("alice");
+        var id = await svc.CreateAsync(Reimb(), isFinance: false);
+        var e = await db.Expenses.FindAsync(id);
+        Assert.Equal("Draft", e!.Status);
+        Assert.Equal("alice", e.SubmittedBy);
+    }
+
+    [Fact]
+    public async Task StateMachine_HappyPath_Submit_Approve_Pay()
+    {
+        var (svc, db, _) = Build("alice");
+        var id = await svc.CreateAsync(Reimb(), isFinance: false);
+        await svc.SubmitAsync(id);
+        Assert.Equal("PendingApproval", (await db.Expenses.FindAsync(id))!.Status);
+        await svc.ApproveAsync(id);
+        Assert.Equal("Approved", (await db.Expenses.FindAsync(id))!.Status);
+        await svc.PayAsync(id, "3001", new DateOnly(2026, 6, 1));
+        var paid = await db.Expenses.FindAsync(id);
+        Assert.Equal("Paid", paid!.Status);
+        Assert.Equal("3001", paid.CheckNumber);
+    }
+
+    [Fact]
+    public async Task Approve_FromDraft_Throws()
+    {
+        var (svc, _, _) = Build("alice");
+        var id = await svc.CreateAsync(Reimb(), isFinance: false);
+        await Assert.ThrowsAsync<InvalidOperationException>(() => svc.ApproveAsync(id));
+    }
+
+    [Fact]
+    public async Task Reject_RecordsNotes_AndStatus()
+    {
+        var (svc, db, _) = Build("alice");
+        var id = await svc.CreateAsync(Reimb(), isFinance: false);
+        await svc.SubmitAsync(id);
+        await svc.RejectAsync(id, "Missing receipt");
+        var e = await db.Expenses.FindAsync(id);
+        Assert.Equal("Rejected", e!.Status);
+        Assert.Equal("Missing receipt", e.ReviewNotes);
+    }
+
+    [Fact]
+    public async Task Update_OthersDraft_AsNonFinance_Throws()
+    {
+        var (aliceSvc, db, fs) = Build("alice");
+        var id = await aliceSvc.CreateAsync(Reimb(), isFinance: false);
+        var bobSvc = SvcAs(db, fs, "bob");
+        await Assert.ThrowsAsync<InvalidOperationException>(() =>
+            bobSvc.UpdateAsync(id, CloneToUpdate(Reimb()), isFinance: false));
+    }
+
+    [Fact]
+    public async Task SoftDelete_HidesFromQueries()
+    {
+        var (svc, db, _) = Build("alice");
+        var id = await svc.CreateAsync(Reimb(), isFinance: false);
+        await svc.DeleteAsync(id, isFinance: true);
+        Assert.Null(await db.Expenses.FirstOrDefaultAsync(e => e.Id == id));
+    }
+
+    [Fact]
+    public async Task Receipt_SaveThenOpen_RoundTrips()
+    {
+        var (svc, _, _) = Build("alice");
+        var id = await svc.CreateAsync(Reimb(), isFinance: false);
+        using var input = new MemoryStream(Encoding.UTF8.GetBytes("img"));
+        await svc.SaveReceiptAsync(id, input, "r.jpg", isFinance: false);
+        var got = await svc.OpenReceiptAsync(id, isFinance: true);
+        Assert.NotNull(got);
+    }
+}
diff --git a/API/ROLAC.API/Services/ExpenseService.cs b/API/ROLAC.API/Services/ExpenseService.cs
new file mode 100644
index 0000000..dac185d
--- /dev/null
+++ b/API/ROLAC.API/Services/ExpenseService.cs
@@ -0,0 +1,240 @@
+using System.Security.Claims;
+using Microsoft.EntityFrameworkCore;
+using ROLAC.API.Data;
+using ROLAC.API.DTOs.Expense;
+using ROLAC.API.DTOs.Shared;
+using ROLAC.API.Entities;
+using ROLAC.API.Services.Storage;
+
+namespace ROLAC.API.Services;
+
+public class ExpenseService : IExpenseService
+{
+    private readonly AppDbContext _db;
+    private readonly IHttpContextAccessor _http;
+    private readonly IFileStorage _storage;
+
+    public ExpenseService(AppDbContext db, IHttpContextAccessor http, IFileStorage storage)
+    { _db = db; _http = http; _storage = storage; }
+
+    private string CurrentUserId =>
+        _http.HttpContext?.User.FindFirstValue(ClaimTypes.NameIdentifier) ?? "system";
+
+    public async Task<PagedResult<ExpenseListItemDto>> GetPagedAsync(
+        int page, int pageSize, string? search, int? ministryId,
+        int? categoryGroupId, string? status, DateOnly? from, DateOnly? to)
+    {
+        var query = _db.Expenses.AsNoTracking().AsQueryable();
+        if (ministryId.HasValue)      query = query.Where(e => e.MinistryId == ministryId.Value);
+        if (categoryGroupId.HasValue) query = query.Where(e => e.CategoryGroupId == categoryGroupId.Value);
+        if (!string.IsNullOrWhiteSpace(status)) query = query.Where(e => e.Status == status);
+        if (from.HasValue) query = query.Where(e => e.ExpenseDate >= from.Value);
+        if (to.HasValue)   query = query.Where(e => e.ExpenseDate <= to.Value);
+        if (!string.IsNullOrWhiteSpace(search))
+        {
+            var s = search.Trim().ToLower(); var term = search.Trim();
+            query = query.Where(e =>
+                e.Description.ToLower().Contains(s) ||
+                (e.VendorName != null && e.VendorName.ToLower().Contains(s)) ||
+                (e.Member != null && (
+                    (e.Member.FirstName_en + " " + e.Member.LastName_en).ToLower().Contains(s) ||
+                    (e.Member.FirstName_zh != null && e.Member.FirstName_zh.Contains(term)) ||
+                    (e.Member.LastName_zh  != null && e.Member.LastName_zh.Contains(term)))));
+        }
+        return await ProjectPagedAsync(query, page, pageSize);
+    }
+
+    public async Task<PagedResult<ExpenseListItemDto>> GetMineAsync(string userId, string? status, int page, int pageSize)
+    {
+        var query = _db.Expenses.AsNoTracking().Where(e => e.SubmittedBy == userId);
+        if (!string.IsNullOrWhiteSpace(status)) query = query.Where(e => e.Status == status);
+        return await ProjectPagedAsync(query, page, pageSize);
+    }
+
+    private async Task<PagedResult<ExpenseListItemDto>> ProjectPagedAsync(IQueryable<Expense> query, int page, int pageSize)
+    {
+        var total = await query.CountAsync();
+        var rows = await query
+            .OrderByDescending(e => e.ExpenseDate).ThenByDescending(e => e.Id)
+            .Skip((page - 1) * pageSize).Take(pageSize).ToListAsync();
+
+        var minNames = await _db.Ministries.AsNoTracking().ToDictionaryAsync(m => m.Id, m => m.Name_en);
+        var grpNames = await _db.ExpenseCategoryGroups.AsNoTracking().ToDictionaryAsync(g => g.Id, g => g.Name_en);
+        var subNames = await _db.ExpenseSubCategories.AsNoTracking().ToDictionaryAsync(s => s.Id, s => s.Name_en);
+        var memberIds = rows.Where(r => r.MemberId != null).Select(r => r.MemberId!.Value).ToHashSet();
+        var memNames = await _db.Members.AsNoTracking().Where(m => memberIds.Contains(m.Id))
+            .ToDictionaryAsync(m => m.Id, m => $"{m.FirstName_en} {m.LastName_en}");
+
+        var items = rows.Select(e => new ExpenseListItemDto
+        {
+            Id = e.Id, Type = e.Type, Status = e.Status, Amount = e.Amount, Description = e.Description,
+            MinistryId = e.MinistryId, MinistryName = minNames.GetValueOrDefault(e.MinistryId, ""),
+            CategoryGroupId = e.CategoryGroupId, CategoryGroupName = grpNames.GetValueOrDefault(e.CategoryGroupId, ""),
+            SubCategoryId = e.SubCategoryId, SubCategoryName = subNames.GetValueOrDefault(e.SubCategoryId, ""),
+            VendorName = e.VendorName, MemberId = e.MemberId,
+            MemberName = e.MemberId != null ? memNames.GetValueOrDefault(e.MemberId.Value) : null,
+            ExpenseDate = e.ExpenseDate.ToString("yyyy-MM-dd"),
+            HasReceipt = e.ReceiptBlobPath != null,
+        }).ToList();
+
+        return new PagedResult<ExpenseListItemDto> { Items = items, TotalCount = total, Page = page, PageSize = pageSize };
+    }
+
+    public async Task<ExpenseDto?> GetByIdAsync(int id)
+    {
+        var e = await _db.Expenses.AsNoTracking().FirstOrDefaultAsync(x => x.Id == id);
+        if (e is null) return null;
+        var minName = await _db.Ministries.Where(m => m.Id == e.MinistryId).Select(m => m.Name_en).FirstOrDefaultAsync() ?? "";
+        var grpName = await _db.ExpenseCategoryGroups.Where(g => g.Id == e.CategoryGroupId).Select(g => g.Name_en).FirstOrDefaultAsync() ?? "";
+        var subName = await _db.ExpenseSubCategories.Where(s => s.Id == e.SubCategoryId).Select(s => s.Name_en).FirstOrDefaultAsync() ?? "";
+        string? memName = e.MemberId != null
+            ? await _db.Members.Where(m => m.Id == e.MemberId).Select(m => m.FirstName_en + " " + m.LastName_en).FirstOrDefaultAsync()
+            : null;
+        return new ExpenseDto
+        {
+            Id = e.Id, Type = e.Type, Status = e.Status, Amount = e.Amount, Description = e.Description,
+            MinistryId = e.MinistryId, MinistryName = minName,
+            CategoryGroupId = e.CategoryGroupId, CategoryGroupName = grpName,
+            SubCategoryId = e.SubCategoryId, SubCategoryName = subName,
+            VendorName = e.VendorName, MemberId = e.MemberId, MemberName = memName,
+            ExpenseDate = e.ExpenseDate.ToString("yyyy-MM-dd"), HasReceipt = e.ReceiptBlobPath != null,
+            CheckNumber = e.CheckNumber, Notes = e.Notes, ReviewNotes = e.ReviewNotes,
+            SubmittedBy = e.SubmittedBy, SubmittedAt = e.SubmittedAt, ReviewedAt = e.ReviewedAt, PaidAt = e.PaidAt,
+        };
+    }
+
+    public async Task<int> CreateAsync(CreateExpenseRequest r, bool isFinance)
+    {
+        var e = new Expense
+        {
+            MinistryId = r.MinistryId, CategoryGroupId = r.CategoryGroupId, SubCategoryId = r.SubCategoryId,
+            Type = r.Type, Amount = r.Amount, Description = r.Description, VendorName = r.VendorName,
+            CheckNumber = r.CheckNumber, ExpenseDate = r.ExpenseDate, Notes = r.Notes,
+        };
+
+        if (r.Type == "VendorPayment")
+        {
+            if (!isFinance) throw new InvalidOperationException("Only finance can create vendor payments.");
+            e.Status = "Paid";
+            e.PaidAt = DateTimeOffset.UtcNow; e.PaidBy = CurrentUserId;
+            e.MemberId = null;
+        }
+        else // StaffReimbursement
+        {
+            e.Status = "Draft";
+            e.SubmittedBy = CurrentUserId;
+            e.MemberId = isFinance ? r.MemberId : await CallerMemberIdAsync();
+            e.VendorName = null;
+        }
+
+        _db.Expenses.Add(e);
+        await _db.SaveChangesAsync();
+        return e.Id;
+    }
+
+    private async Task<int?> CallerMemberIdAsync()
+    {
+        var uid = CurrentUserId;
+        return await _db.Users.Where(u => u.Id == uid).Select(u => u.MemberId).FirstOrDefaultAsync();
+    }
+
+    public async Task UpdateAsync(int id, UpdateExpenseRequest r, bool isFinance)
+    {
+        // FirstOrDefaultAsync (not FindAsync) so the soft-delete query filter applies.
+        var e = await _db.Expenses.FirstOrDefaultAsync(x => x.Id == id)
+            ?? throw new KeyNotFoundException($"Expense {id} not found.");
+        if (!isFinance && !(e.SubmittedBy == CurrentUserId && e.Status == "Draft"))
+            throw new InvalidOperationException("You can only edit your own draft reimbursements.");
+
+        e.MinistryId = r.MinistryId; e.CategoryGroupId = r.CategoryGroupId; e.SubCategoryId = r.SubCategoryId;
+        e.Amount = r.Amount; e.Description = r.Description; e.CheckNumber = r.CheckNumber;
+        e.ExpenseDate = r.ExpenseDate; e.Notes = r.Notes;
+        if (e.Type == "VendorPayment") e.VendorName = r.VendorName;
+        await _db.SaveChangesAsync();
+    }
+
+    public async Task DeleteAsync(int id, bool isFinance)
+    {
+        var e = await _db.Expenses.FirstOrDefaultAsync(x => x.Id == id)
+            ?? throw new KeyNotFoundException($"Expense {id} not found.");
+        if (!isFinance && !(e.SubmittedBy == CurrentUserId && e.Status == "Draft"))
+            throw new InvalidOperationException("You can only delete your own draft reimbursements.");
+        e.IsDeleted = true; e.DeletedAt = DateTimeOffset.UtcNow; e.DeletedBy = CurrentUserId;
+        await _db.SaveChangesAsync();
+    }
+
+    // FirstOrDefaultAsync (not FindAsync) so the soft-delete query filter applies.
+    private async Task<Expense> RequireAsync(int id) =>
+        await _db.Expenses.FirstOrDefaultAsync(x => x.Id == id)
+            ?? throw new KeyNotFoundException($"Expense {id} not found.");
+
+    public async Task SubmitAsync(int id)
+    {
+        var e = await RequireAsync(id);
+        if (e.SubmittedBy != CurrentUserId) throw new InvalidOperationException("Only the submitter can submit this reimbursement.");
+        if (e.Status != "Draft") throw new InvalidOperationException($"Cannot submit from status '{e.Status}'.");
+        e.Status = "PendingApproval"; e.SubmittedAt = DateTimeOffset.UtcNow;
+        await _db.SaveChangesAsync();
+    }
+
+    public async Task ApproveAsync(int id)
+    {
+        var e = await RequireAsync(id);
+        if (e.Status != "PendingApproval") throw new InvalidOperationException($"Cannot approve from status '{e.Status}'.");
+        e.Status = "Approved"; e.ReviewedBy = CurrentUserId; e.ReviewedAt = DateTimeOffset.UtcNow;
+        await _db.SaveChangesAsync();
+    }
+
+    public async Task RejectAsync(int id, string? reviewNotes)
+    {
+        var e = await RequireAsync(id);
+        if (e.Status != "PendingApproval") throw new InvalidOperationException($"Cannot reject from status '{e.Status}'.");
+        e.Status = "Rejected"; e.ReviewedBy = CurrentUserId; e.ReviewedAt = DateTimeOffset.UtcNow; e.ReviewNotes = reviewNotes;
+        await _db.SaveChangesAsync();
+    }
+
+    public async Task PayAsync(int id, string? checkNumber, DateOnly? paidAt)
+    {
+        var e = await RequireAsync(id);
+        if (e.Status != "Approved") throw new InvalidOperationException($"Cannot mark paid from status '{e.Status}'.");
+        e.Status = "Paid";
+        if (!string.IsNullOrWhiteSpace(checkNumber)) e.CheckNumber = checkNumber;
+        e.PaidBy = CurrentUserId;
+        e.PaidAt = paidAt.HasValue
+            ? new DateTimeOffset(paidAt.Value.ToDateTime(TimeOnly.MinValue), TimeSpan.Zero)
+            : DateTimeOffset.UtcNow;
+        await _db.SaveChangesAsync();
+    }
+
+    public async Task SaveReceiptAsync(int id, Stream content, string fileName, bool isFinance)
+    {
+        var e = await RequireAsync(id);
+        if (!isFinance && e.SubmittedBy != CurrentUserId)
+            throw new InvalidOperationException("You can only attach receipts to your own reimbursements.");
+
+        var safe = Path.GetFileName(fileName).Replace(' ', '_');
+        var path = $"finance/receipts/{e.ExpenseDate.Year}/{e.ExpenseDate.Month}/{e.Id}-{safe}";
+        if (e.ReceiptBlobPath != null && e.ReceiptBlobPath != path)
+            await _storage.DeleteAsync(e.ReceiptBlobPath);
+        var saved = await _storage.SaveAsync(content, path);
+        e.ReceiptBlobPath = saved;
+        await _db.SaveChangesAsync();
+    }
+
+    public async Task<(Stream stream, string contentType)?> OpenReceiptAsync(int id, bool isFinance)
+    {
+        var e = await RequireAsync(id);
+        if (!isFinance && e.SubmittedBy != CurrentUserId)
+            throw new InvalidOperationException("Not authorized to view this receipt.");
+        if (e.ReceiptBlobPath is null) return null;
+        var stream = await _storage.OpenReadAsync(e.ReceiptBlobPath);
+        if (stream is null) return null;
+        var ext = Path.GetExtension(e.ReceiptBlobPath).ToLowerInvariant();
+        var contentType = ext switch
+        {
+            ".png" => "image/png", ".webp" => "image/webp", ".pdf" => "application/pdf",
+            _ => "image/jpeg",
+        };
+        return (stream, contentType);
+    }
+}
diff --git a/API/ROLAC.API/Services/IExpenseService.cs b/API/ROLAC.API/Services/IExpenseService.cs
new file mode 100644
index 0000000..89e068f
--- /dev/null
+++ b/API/ROLAC.API/Services/IExpenseService.cs
@@ -0,0 +1,21 @@
+using ROLAC.API.DTOs.Expense;
+using ROLAC.API.DTOs.Shared;
+namespace ROLAC.API.Services;
+
+public interface IExpenseService
+{
+    Task<PagedResult<ExpenseListItemDto>> GetPagedAsync(
+        int page, int pageSize, string? search, int? ministryId,
+        int? categoryGroupId, string? status, DateOnly? from, DateOnly? to);
+    Task<PagedResult<ExpenseListItemDto>> GetMineAsync(string userId, string? status, int page, int pageSize);
+    Task<ExpenseDto?> GetByIdAsync(int id);
+    Task<int> CreateAsync(CreateExpenseRequest r, bool isFinance);
+    Task UpdateAsync(int id, UpdateExpenseRequest r, bool isFinance);
+    Task DeleteAsync(int id, bool isFinance);
+    Task SubmitAsync(int id);
+    Task ApproveAsync(int id);
+    Task RejectAsync(int id, string? reviewNotes);
+    Task PayAsync(int id, string? checkNumber, DateOnly? paidAt);
+    Task SaveReceiptAsync(int id, Stream content, string fileName, bool isFinance);
+    Task<(Stream stream, string contentType)?> OpenReceiptAsync(int id, bool isFinance);
+}