diff --git a/desktop/src/main/java/org/example/petshopdesktop/controllers/SaleController.java b/desktop/src/main/java/org/example/petshopdesktop/controllers/SaleController.java
index 7e80c531..22c96dbd 100644
--- a/desktop/src/main/java/org/example/petshopdesktop/controllers/SaleController.java
+++ b/desktop/src/main/java/org/example/petshopdesktop/controllers/SaleController.java
@@ -258,18 +258,23 @@ public class SaleController {
 
                     if (sale.getItems() != null && !sale.getItems().isEmpty()) {
                         for (SaleItemResponse item : sale.getItems()) {
+                            boolean isRefund = sale.getIsRefund() != null && sale.getIsRefund();
                             double unitPrice = item.getUnitPrice() != null ? item.getUnitPrice().doubleValue() : 0.0;
-                            double lineTotal = unitPrice * item.getQuantity();
+                            int quantity = item.getQuantity() != null ? item.getQuantity() : 0;
+                            if (isRefund && quantity > 0) {
+                                quantity = -quantity;
+                            }
+                            double lineTotal = unitPrice * quantity;
                             lineItems.add(new SaleLineItem(
                                 sale.getSaleId().intValue(),
                                 saleDate,
                                 sale.getEmployeeName(),
                                 item.getProductName(),
-                                item.getQuantity(),
+                                quantity,
                                 unitPrice,
                                 lineTotal,
                                 sale.getPaymentMethod(),
-                                sale.getIsRefund() != null && sale.getIsRefund()
+                                isRefund
                             ));
                         }
                     }
@@ -501,9 +506,13 @@ public class SaleController {
     private SaleDetail mapToSaleDetail(SaleResponse sale) {
         ObservableList<SaleDetail.SaleDetailItem> items = FXCollections.observableArrayList();
         if (sale.getItems() != null) {
+            boolean isRefund = sale.getIsRefund() != null && sale.getIsRefund();
             for (SaleItemResponse item : sale.getItems()) {
                 double unitPrice = item.getUnitPrice() != null ? item.getUnitPrice().doubleValue() : 0.0;
                 int quantity = item.getQuantity() != null ? item.getQuantity() : 0;
+                if (isRefund && quantity > 0) {
+                    quantity = -quantity;
+                }
                 items.add(new SaleDetail.SaleDetailItem(
                     item.getProdId() != null ? item.getProdId().intValue() : 0,
                     item.getProductName(),