diff --git a/API/ROLAC.API.Tests/Services/OfferingSessionServiceTests.cs b/API/ROLAC.API.Tests/Services/OfferingSessionServiceTests.cs
index 4e9593e..824fd45 100644
--- a/API/ROLAC.API.Tests/Services/OfferingSessionServiceTests.cs
+++ b/API/ROLAC.API.Tests/Services/OfferingSessionServiceTests.cs
@@ -129,4 +129,27 @@ public class OfferingSessionServiceTests
         Assert.Equal(200m, after.SystemTotal);
         Assert.Equal(1, await db.Givings.CountAsync(g => g.OfferingSessionId == id));
     }
+
+    [Fact]
+    public async Task GetByIdAsync_ReturnsCheckZelleAndPayPalRefs()
+    {
+        using var db = BuildDb();
+        var catId = await SeedCategoryAsync(db);
+        var svc = new OfferingSessionService(db, BuildAccessor());
+        var req = new CreateOfferingSessionRequest
+        {
+            SessionDate = new DateOnly(2026, 6, 7), CashTotal = 0m, CheckTotal = 100m,
+            Givings = [ new() { GivingCategoryId = catId, Amount = 100m, PaymentMethod = "Zelle",
+                ZelleReferenceCode = "Z-123", PayPalTransactionId = "PP-456", CheckNumber = "C-789" } ],
+        };
+        var id = await svc.CreateAsync(req);
+
+        var dto = await svc.GetByIdAsync(id);
+
+        Assert.NotNull(dto);
+        var line = Assert.Single(dto!.Givings);
+        Assert.Equal("Z-123", line.ZelleReferenceCode);
+        Assert.Equal("PP-456", line.PayPalTransactionId);
+        Assert.Equal("C-789", line.CheckNumber);
+    }
 }
diff --git a/API/ROLAC.API/DTOs/Giving/OfferingGivingLineDto.cs b/API/ROLAC.API/DTOs/Giving/OfferingGivingLineDto.cs
index 28c822b..687f474 100644
--- a/API/ROLAC.API/DTOs/Giving/OfferingGivingLineDto.cs
+++ b/API/ROLAC.API/DTOs/Giving/OfferingGivingLineDto.cs
@@ -10,6 +10,8 @@ public class OfferingGivingLineDto
     public decimal Amount           { get; set; }
     public string  PaymentMethod    { get; set; } = "";
     public string? CheckNumber      { get; set; }
+    public string? ZelleReferenceCode  { get; set; }
+    public string? PayPalTransactionId { get; set; }
     public bool    IsAnonymous      { get; set; }
     public string? Notes            { get; set; }
 }
diff --git a/API/ROLAC.API/Services/OfferingSessionService.cs b/API/ROLAC.API/Services/OfferingSessionService.cs
index 6b7df50..c90b368 100644
--- a/API/ROLAC.API/Services/OfferingSessionService.cs
+++ b/API/ROLAC.API/Services/OfferingSessionService.cs
@@ -57,6 +57,10 @@ public class OfferingSessionService : IOfferingSessionService
     public async Task<bool> DateExistsAsync(DateOnly date)
         => await _db.OfferingSessions.AnyAsync(s => s.SessionDate == date);
 
+    // Distinguishes a unique-index collision on SessionDate (concurrent insert) from other DB errors.
+    private async Task<bool> DateExistsConcurrentlyAsync(DateOnly date, int excludeId)
+        => await _db.OfferingSessions.AsNoTracking().AnyAsync(s => s.SessionDate == date && s.Id != excludeId);
+
     public async Task<OfferingSessionDto?> GetByIdAsync(int id)
     {
         var s = await _db.OfferingSessions.AsNoTracking().FirstOrDefaultAsync(x => x.Id == id);
@@ -84,7 +88,10 @@ public class OfferingSessionService : IOfferingSessionService
                 GivingCategoryId = l.GivingCategoryId,
                 CategoryName = catNames.TryGetValue(l.GivingCategoryId, out var cn) ? cn : "",
                 Amount = l.Amount, PaymentMethod = l.PaymentMethod,
-                CheckNumber = l.CheckNumber, IsAnonymous = l.IsAnonymous, Notes = l.Notes,
+                CheckNumber = l.CheckNumber,
+                ZelleReferenceCode = l.ZelleReferenceCode,
+                PayPalTransactionId = l.PayPalTransactionId,
+                IsAnonymous = l.IsAnonymous, Notes = l.Notes,
             }).ToList(),
         };
     }
@@ -106,7 +113,16 @@ public class OfferingSessionService : IOfferingSessionService
             Givings = r.Givings.Select(line => MapLine(line, r.SessionDate)).ToList(),
         };
         _db.OfferingSessions.Add(session);
-        await _db.SaveChangesAsync();
+        try
+        {
+            await _db.SaveChangesAsync();
+        }
+        catch (DbUpdateException)
+        {
+            if (await DateExistsConcurrentlyAsync(r.SessionDate, session.Id))
+                throw new InvalidOperationException($"An offering session for {r.SessionDate:yyyy-MM-dd} already exists.");
+            throw;
+        }
         return session.Id;
     }