diff --git a/invoice_service.py b/invoice_service.py
index 51c4aab..b2e3a40 100644
--- a/invoice_service.py
+++ b/invoice_service.py
@@ -32,12 +32,12 @@ def extract_invoice_data(text):
         seller_name = seller_match.group(1).strip() if seller_match else None
 
         nip_match = re.search(r'(?i)Sprzedawca:.*?NIP:\s*(\d+)', text, re.DOTALL)
-        vat_id = nip_match.group(1) if nip_match else None
+        seller_nip = nip_match.group(1) if nip_match else None
 
         total = extract_total(text)
 
         return {
-            "vat_id": vat_id,
+            "seller_nip": seller_nip,
             "seller_name": seller_name,
             "total": total
         }