diff --git a/API/ROLAC.API.Tests/Services/ExpenseSnapshotServiceTests.cs b/API/ROLAC.API.Tests/Services/ExpenseSnapshotServiceTests.cs
index d8918b7..a0b0e0e 100644
--- a/API/ROLAC.API.Tests/Services/ExpenseSnapshotServiceTests.cs
+++ b/API/ROLAC.API.Tests/Services/ExpenseSnapshotServiceTests.cs
@@ -32,7 +32,12 @@ public class ExpenseSnapshotServiceTests
         db.ExpenseCategoryGroups.Add(new ExpenseCategoryGroup { Id = 1, Name_en = "Facilities" });
         db.ExpenseSubCategories.Add(new ExpenseSubCategory { Id = 1, GroupId = 1, Name_en = "Rent" });
         db.SaveChanges();
-        return (new ExpenseSnapshotService(db), db);
+
+        var claims = new[] { new Claim(ClaimTypes.NameIdentifier, userId) };
+        var ctx    = new DefaultHttpContext { User = new(new ClaimsIdentity(claims)) };
+        var http   = new Mock<IHttpContextAccessor>();
+        http.Setup(x => x.HttpContext).Returns(ctx);
+        return (new ExpenseSnapshotService(db, http.Object), db);
     }
 
     private static CreateExpenseSnapshotRequest Rent() => new()
@@ -62,6 +67,15 @@ public class ExpenseSnapshotServiceTests
         await Assert.ThrowsAsync<InvalidOperationException>(() => svc.CreateAsync(r));
     }
 
+    [Fact]
+    public async Task Create_WithInvalidFunctionalClass_Throws()
+    {
+        var (svc, _) = Build();
+        var r = Rent();
+        r.Lines[0].FunctionalClass = "NotAClass";
+        await Assert.ThrowsAsync<InvalidOperationException>(() => svc.CreateAsync(r));
+    }
+
     [Fact]
     public async Task GetById_ReturnsLines_TotalsAndCreatorName()
     {
@@ -138,4 +152,14 @@ public class ExpenseSnapshotServiceTests
         Assert.Empty(await svc.GetAllAsync());
         Assert.Null(await db.ExpenseSnapshots.FirstOrDefaultAsync(s => s.Id == id));
     }
+
+    [Fact]
+    public async Task Delete_StampsDeletedBy()
+    {
+        var (svc, db) = Build("deleter-1");
+        var id = await svc.CreateAsync(Rent());
+        await svc.DeleteAsync(id);
+        var row = await db.ExpenseSnapshots.IgnoreQueryFilters().FirstAsync(s => s.Id == id);
+        Assert.Equal("deleter-1", row.DeletedBy);
+    }
 }
diff --git a/API/ROLAC.API/Services/ExpenseSnapshotService.cs b/API/ROLAC.API/Services/ExpenseSnapshotService.cs
index cd85877..3df66bb 100644
--- a/API/ROLAC.API/Services/ExpenseSnapshotService.cs
+++ b/API/ROLAC.API/Services/ExpenseSnapshotService.cs
@@ -1,3 +1,5 @@
+using System.Security.Claims;
+using Microsoft.AspNetCore.Http;
 using Microsoft.EntityFrameworkCore;
 using ROLAC.API.Data;
 using ROLAC.API.DTOs.Expense;
@@ -8,7 +10,17 @@ namespace ROLAC.API.Services;
 public class ExpenseSnapshotService : IExpenseSnapshotService
 {
     private readonly AppDbContext _db;
-    public ExpenseSnapshotService(AppDbContext db) => _db = db;
+    private readonly IHttpContextAccessor _http;
+    public ExpenseSnapshotService(AppDbContext db, IHttpContextAccessor http)
+    { _db = db; _http = http; }
+
+    // The JWT carries the user id in the "sub" claim (NameClaimType="sub", MapInboundClaims=false),
+    // so ClaimTypes.NameIdentifier is absent at runtime. Check NameIdentifier first (unit tests set it),
+    // then fall back to "sub" (real tokens). Required for the self-ownership guard to work in production.
+    private string CurrentUserId =>
+        _http.HttpContext?.User.FindFirstValue(ClaimTypes.NameIdentifier)
+        ?? _http.HttpContext?.User.FindFirstValue("sub")
+        ?? "system";
 
     public async Task<List<ExpenseSnapshotDto>> GetAllAsync()
     {
@@ -101,7 +113,7 @@ public class ExpenseSnapshotService : IExpenseSnapshotService
     {
         var s = await _db.ExpenseSnapshots.FirstOrDefaultAsync(x => x.Id == id)
             ?? throw new KeyNotFoundException($"Snapshot {id} not found.");
-        s.IsDeleted = true; s.DeletedAt = DateTimeOffset.UtcNow;
+        s.IsDeleted = true; s.DeletedAt = DateTimeOffset.UtcNow; s.DeletedBy = CurrentUserId;
         await _db.SaveChangesAsync();
     }
 
@@ -115,6 +127,8 @@ public class ExpenseSnapshotService : IExpenseSnapshotService
                 throw new InvalidOperationException("Each snapshot line needs a category group and subcategory.");
             if (l.Amount <= 0)
                 throw new InvalidOperationException("Each snapshot line amount must be greater than zero.");
+            if (l.FunctionalClass is not null && !FunctionalClasses.All.Contains(l.FunctionalClass))
+                throw new InvalidOperationException($"Invalid functional class '{l.FunctionalClass}'.");
         }
     }