diff --git a/uncloud_django_based/uncloud/uncloud_pay/views.py b/uncloud_django_based/uncloud/uncloud_pay/views.py
index 82b5787..59d310e 100644
--- a/uncloud_django_based/uncloud/uncloud_pay/views.py
+++ b/uncloud_django_based/uncloud/uncloud_pay/views.py
@@ -215,10 +215,11 @@ class BillingAddressViewSet(mixins.CreateModelMixin,
 
         # Validate VAT numbers.
         country = serializer.validated_data["country"]
-        vat_number = serializer.validated_data["vat_number"]
 
         # We ignore empty VAT numbers.
-        if vat_number != "":
+        if 'vat_number' in serializer.validated_data and serializer.validated_data["vat_number"] != "":
+            vat_number = serializer.validated_data["vat_number"]
+
             if not validate_vat(country, vat_number):
                 return Response(
                     {'error': 'Malformed VAT number.'},