diff --git a/frontend/src/components/domain/onboarding/steps/UploadSalesDataStep.tsx b/frontend/src/components/domain/onboarding/steps/UploadSalesDataStep.tsx
index 59d43cce..646a6f4b 100644
--- a/frontend/src/components/domain/onboarding/steps/UploadSalesDataStep.tsx
+++ b/frontend/src/components/domain/onboarding/steps/UploadSalesDataStep.tsx
@@ -455,13 +455,19 @@ export const UploadSalesDataStep: React.FC<UploadSalesDataStepProps> = ({
     try {
       // Create all ingredients in parallel
       const creationPromises = inventoryItems.map(item => {
+        // Normalize unit to lowercase (backend requires lowercase)
+        const normalizedUnit = item.unit_of_measure.toLowerCase();
+
+        // Ensure max_stock_level is at least 1 (backend validation requires > 0)
+        const maxStockLevel = Math.max(1, item.stock_quantity * 2);
+
         const ingredientData = {
           name: item.name,
           product_type: item.product_type,
           category: item.category,
-          unit_of_measure: item.unit_of_measure,
+          unit_of_measure: normalizedUnit,
           low_stock_threshold: item.low_stock_threshold,
-          max_stock_level: item.stock_quantity * 2,
+          max_stock_level: maxStockLevel,
           reorder_point: item.reorder_point,
           shelf_life_days: item.estimated_shelf_life_days,
           requires_refrigeration: item.requires_refrigeration,