diff --git a/apps/web-client-tpos-net/src/WebClientTpos.Client/Pages/Pos/Cafe/CafeDesktop.razor b/apps/web-client-tpos-net/src/WebClientTpos.Client/Pages/Pos/Cafe/CafeDesktop.razor
index ce967c37..2fb4f001 100644
--- a/apps/web-client-tpos-net/src/WebClientTpos.Client/Pages/Pos/Cafe/CafeDesktop.razor
+++ b/apps/web-client-tpos-net/src/WebClientTpos.Client/Pages/Pos/Cafe/CafeDesktop.razor
@@ -209,8 +209,19 @@
                             </div>
                         </div>
                         <div style="padding:16px;border-top:1px solid var(--pos-border-subtle);">
-                            <button class="pos-btn-checkout" @onclick="ConfirmPayment" disabled="@(_receivedAmount < FinalTotal)">
-                                Xác nhận thanh toán
+                            @if (!string.IsNullOrEmpty(_paymentError))
+                            {
+                                <div style="font-size:12px;color:var(--pos-danger);margin-bottom:8px;text-align:center;">@_paymentError</div>
+                            }
+                            <button class="pos-btn-checkout" @onclick="ConfirmPayment" disabled="@(_receivedAmount < FinalTotal || _paymentProcessing)">
+                                @if (_paymentProcessing)
+                                {
+                                    <span>Đang xử lý...</span>
+                                }
+                                else
+                                {
+                                    <span>Xác nhận thanh toán</span>
+                                }
                             </button>
                         </div>
                     </div>
@@ -246,8 +257,19 @@
                             }
                         </div>
                         <div style="padding:16px;border-top:1px solid var(--pos-border-subtle);">
-                            <button class="pos-btn-checkout" @onclick="ConfirmPayment">
-                                Xác nhận đã thanh toán
+                            @if (!string.IsNullOrEmpty(_paymentError))
+                            {
+                                <div style="font-size:12px;color:var(--pos-danger);margin-bottom:8px;text-align:center;">@_paymentError</div>
+                            }
+                            <button class="pos-btn-checkout" @onclick="ConfirmPayment" disabled="@_paymentProcessing">
+                                @if (_paymentProcessing)
+                                {
+                                    <span>Đang xử lý...</span>
+                                }
+                                else
+                                {
+                                    <span>Xác nhận đã thanh toán</span>
+                                }
                             </button>
                         </div>
                     </div>
@@ -932,11 +954,13 @@
     }
 
     private bool _paymentProcessing;
+    private string? _paymentError;
 
     private async Task ConfirmPayment()
     {
         if (_paymentProcessing) return;
         _paymentProcessing = true;
+        _paymentError = null;
         StateHasChanged();
 
         _lastOrderTotal = FinalTotal;
@@ -946,16 +970,26 @@
 
         // EN: Call API to mark order as paid (order was already created in StartPayment)
         // VI: Gọi API đánh dấu đơn đã thanh toán (đơn đã được tạo ở StartPayment)
+        bool paymentSuccess = false;
         try
         {
             if (_createdOrderId.HasValue)
             {
-                await DataService.PayOrderAsync(_createdOrderId.Value, ShopId, _selectedMethod);
+                // EN: Pass amountTendered for cash (required by validator), use FinalTotal for non-cash
+                // VI: Truyền amountTendered cho tiền mặt (validator yêu cầu), dùng FinalTotal cho phương thức khác
+                var amount = _selectedMethod == "cash" ? _receivedAmount : FinalTotal;
+                var result = await DataService.PayOrderWithDetailsAsync(
+                    _createdOrderId.Value, ShopId, _selectedMethod, amount);
+                paymentSuccess = result?.Success ?? false;
                 _lastTransactionId = _createdOrderId.Value.ToString()[..8].ToUpper();
             }
-            else
+
+            if (!paymentSuccess)
             {
-                _lastTransactionId = $"POS-{DateTime.Now:yyyyMMdd}-{DateTime.Now:HHmmss}";
+                _paymentError = "Thanh toán thất bại. Vui lòng thử lại.";
+                _paymentProcessing = false;
+                StateHasChanged();
+                return;
             }
 
             // EN: Redeem voucher if applied / VI: Sử dụng voucher nếu đã áp dụng
@@ -964,11 +998,12 @@
                 try { await DataService.RedeemVoucherAsync(_appliedVoucher.VoucherId.Value, _discountAmount); } catch { }
             }
         }
-        catch
+        catch (Exception ex)
         {
-            // EN: Fallback — generate local ID if API fails
-            // VI: Fallback — tạo ID local nếu API lỗi
-            _lastTransactionId = $"POS-{DateTime.Now:yyyyMMdd}-{DateTime.Now:HHmmss}";
+            _paymentError = $"Lỗi thanh toán: {ex.Message}. Vui lòng thử lại.";
+            _paymentProcessing = false;
+            StateHasChanged();
+            return;
         }
 
         // EN: Save to session history (in-memory for this POS session)
diff --git a/apps/web-client-tpos-net/src/WebClientTpos.Client/Pages/Pos/Cafe/CafeMobile.razor b/apps/web-client-tpos-net/src/WebClientTpos.Client/Pages/Pos/Cafe/CafeMobile.razor
index 49beed38..57ea4fd8 100644
--- a/apps/web-client-tpos-net/src/WebClientTpos.Client/Pages/Pos/Cafe/CafeMobile.razor
+++ b/apps/web-client-tpos-net/src/WebClientTpos.Client/Pages/Pos/Cafe/CafeMobile.razor
@@ -518,27 +518,37 @@
     }
 
     private bool _paymentProcessing;
+    private string? _paymentError;
 
     private async Task ConfirmPayment()
     {
         if (_paymentProcessing) return;
         _paymentProcessing = true;
+        _paymentError = null;
         StateHasChanged();
 
         _lastOrderTotal = FinalTotal;
         _lastPaymentMethod = _selectedMethod;
         _lastReceiptItems = _cartItems.Select(i => (i.Name, i.Qty, i.Price)).ToList();
 
+        bool paymentSuccess = false;
         try
         {
             if (_createdOrderId.HasValue)
             {
-                await DataService.PayOrderAsync(_createdOrderId.Value, ShopId);
+                var amount = _selectedMethod == "cash" ? _receivedAmount : FinalTotal;
+                var result = await DataService.PayOrderWithDetailsAsync(
+                    _createdOrderId.Value, ShopId, _selectedMethod, amount);
+                paymentSuccess = result?.Success ?? false;
                 _lastTransactionId = _createdOrderId.Value.ToString()[..8].ToUpper();
             }
-            else
+
+            if (!paymentSuccess)
             {
-                _lastTransactionId = $"POS-{DateTime.Now:yyyyMMdd}-{DateTime.Now:HHmmss}";
+                _paymentError = "Thanh toán thất bại. Vui lòng thử lại.";
+                _paymentProcessing = false;
+                StateHasChanged();
+                return;
             }
 
             if (_appliedVoucher?.VoucherId != null && _discountAmount > 0)
@@ -546,9 +556,12 @@
                 try { await DataService.RedeemVoucherAsync(_appliedVoucher.VoucherId.Value, _discountAmount); } catch { }
             }
         }
-        catch
+        catch (Exception ex)
         {
-            _lastTransactionId = $"POS-{DateTime.Now:yyyyMMdd}-{DateTime.Now:HHmmss}";
+            _paymentError = $"Lỗi thanh toán: {ex.Message}. Vui lòng thử lại.";
+            _paymentProcessing = false;
+            StateHasChanged();
+            return;
         }
 
         _paymentProcessing = false;
diff --git a/apps/web-client-tpos-net/src/WebClientTpos.Client/Pages/Pos/Cafe/CafeTablet.razor b/apps/web-client-tpos-net/src/WebClientTpos.Client/Pages/Pos/Cafe/CafeTablet.razor
index 23eb0331..4eb47a59 100644
--- a/apps/web-client-tpos-net/src/WebClientTpos.Client/Pages/Pos/Cafe/CafeTablet.razor
+++ b/apps/web-client-tpos-net/src/WebClientTpos.Client/Pages/Pos/Cafe/CafeTablet.razor
@@ -495,27 +495,37 @@
     }
 
     private bool _paymentProcessing;
+    private string? _paymentError;
 
     private async Task ConfirmPayment()
     {
         if (_paymentProcessing) return;
         _paymentProcessing = true;
+        _paymentError = null;
         StateHasChanged();
 
         _lastOrderTotal = FinalTotal;
         _lastPaymentMethod = _selectedMethod;
         _lastReceiptItems = _cartItems.Select(i => (i.Name, i.Qty, i.Price)).ToList();
 
+        bool paymentSuccess = false;
         try
         {
             if (_createdOrderId.HasValue)
             {
-                await DataService.PayOrderAsync(_createdOrderId.Value, ShopId);
+                var amount = _selectedMethod == "cash" ? _receivedAmount : FinalTotal;
+                var result = await DataService.PayOrderWithDetailsAsync(
+                    _createdOrderId.Value, ShopId, _selectedMethod, amount);
+                paymentSuccess = result?.Success ?? false;
                 _lastTransactionId = _createdOrderId.Value.ToString()[..8].ToUpper();
             }
-            else
+
+            if (!paymentSuccess)
             {
-                _lastTransactionId = $"POS-{DateTime.Now:yyyyMMdd}-{DateTime.Now:HHmmss}";
+                _paymentError = "Thanh toán thất bại. Vui lòng thử lại.";
+                _paymentProcessing = false;
+                StateHasChanged();
+                return;
             }
 
             if (_appliedVoucher?.VoucherId != null && _discountAmount > 0)
@@ -523,9 +533,12 @@
                 try { await DataService.RedeemVoucherAsync(_appliedVoucher.VoucherId.Value, _discountAmount); } catch { }
             }
         }
-        catch
+        catch (Exception ex)
         {
-            _lastTransactionId = $"POS-{DateTime.Now:yyyyMMdd}-{DateTime.Now:HHmmss}";
+            _paymentError = $"Lỗi thanh toán: {ex.Message}. Vui lòng thử lại.";
+            _paymentProcessing = false;
+            StateHasChanged();
+            return;
         }
 
         _paymentProcessing = false;
diff --git a/apps/web-client-tpos-net/src/WebClientTpos.Client/Pages/Pos/Restaurant/RestaurantDesktop.razor b/apps/web-client-tpos-net/src/WebClientTpos.Client/Pages/Pos/Restaurant/RestaurantDesktop.razor
index ee6cd0dc..cc879a36 100644
--- a/apps/web-client-tpos-net/src/WebClientTpos.Client/Pages/Pos/Restaurant/RestaurantDesktop.razor
+++ b/apps/web-client-tpos-net/src/WebClientTpos.Client/Pages/Pos/Restaurant/RestaurantDesktop.razor
@@ -674,10 +674,13 @@
             _receivedAmount = val;
     }
 
+    private string? _paymentError;
+
     private async Task ConfirmPayment()
     {
         if (_paymentProcessing || SelectedTable == null) return;
         _paymentProcessing = true;
+        _paymentError = null;
         StateHasChanged();
 
         _lastOrderTotal = GrandTotal;
@@ -686,10 +689,34 @@
         _lastTransactionId = $"POS-{DateTime.Now:yyyyMMdd}-{DateTime.Now:HHmmss}";
 
         // Pay all orders for this table in the backend
-        if (_tableOrderIds.TryGetValue(SelectedTable.Id, out var orderIds))
+        bool allPaid = true;
+        try
         {
-            foreach (var orderId in orderIds)
-                await DataService.PayOrderAsync(orderId, ShopId);
+            if (_tableOrderIds.TryGetValue(SelectedTable.Id, out var orderIds))
+            {
+                var amount = _selectedMethod == "cash" ? _receivedAmount : GrandTotal;
+                foreach (var orderId in orderIds)
+                {
+                    var result = await DataService.PayOrderWithDetailsAsync(
+                        orderId, ShopId, _selectedMethod, amount);
+                    if (result?.Success != true) allPaid = false;
+                }
+            }
+
+            if (!allPaid)
+            {
+                _paymentError = "Thanh toán thất bại. Vui lòng thử lại.";
+                _paymentProcessing = false;
+                StateHasChanged();
+                return;
+            }
+        }
+        catch (Exception ex)
+        {
+            _paymentError = $"Lỗi thanh toán: {ex.Message}. Vui lòng thử lại.";
+            _paymentProcessing = false;
+            StateHasChanged();
+            return;
         }
 
         _paymentProcessing = false;