diff --git a/services/dataProcessor.ts b/services/dataProcessor.ts
index 2a8168d..b1ac171 100644
--- a/services/dataProcessor.ts
+++ b/services/dataProcessor.ts
@@ -307,11 +307,16 @@ const isAllowedCustomer = (customer: string): boolean => {
     if (!customer) return false;
     const normCustomer = customer.trim().toLowerCase();
     
-    // Use strict equality to prevent loose matches (e.g., 'UK' matching 'Amazon UK')
-    // which incorrectly included ad spend records in sell-out totals.
-    return ALLOWED_CUSTOMERS.some(allowed => 
-        normCustomer === allowed.toLowerCase()
-    );
+    // Strict business rule: Only records from recognized Amazon marketplaces are included in Sell-Out revenue.
+    // This excludes marketing spend, financial adjustments, and non-Amazon channels.
+    const isAmazon = normCustomer.startsWith('amazon') || normCustomer === 'pan-eu';
+    
+    // Additional check: Ensure it's not JUST a country code (often used in ad-spend records)
+    const isOnlyCountryCode = ['uk', 'de', 'it', 'fr', 'es', 'nl', 'se', 'pl', 'be'].includes(normCustomer);
+
+    if (isOnlyCountryCode && !normCustomer.startsWith('amazon')) return false;
+
+    return isAmazon;
 };
 
 // --- SALES / SELL OUT MAPPING ---