diff --git a/inventory/models.py b/inventory/models.py
index 0a9feba5..6b4e3619 100644
--- a/inventory/models.py
+++ b/inventory/models.py
@@ -2742,6 +2742,21 @@ class Vendor(models.Model, LocalizedNameMixin):
             models.Index(fields=["crn"], name="vendor_crn_idx"),
             models.Index(fields=["vrn"], name="vendor_vrn_idx"),
         ]
+        constraints = [
+            models.UniqueConstraint(
+                fields=["dealer", "crn"], name="unique_crn_per_dealer"
+            ),
+            models.UniqueConstraint(
+                fields=["dealer", "vrn"], name="unique_vrn_per_dealer"
+            ),
+            models.UniqueConstraint(
+                fields=["dealer", "email"], name="unique_email_per_dealer"
+            ),
+            models.UniqueConstraint(
+                fields=["dealer", "phone_number"], name="unique_phone_number_per_dealer"
+            ),
+        ]
+
 
     def __str__(self):
         return self.name
diff --git a/inventory/views.py b/inventory/views.py
index f9be7e6c..79b7aaf3 100644
--- a/inventory/views.py
+++ b/inventory/views.py
@@ -3654,7 +3654,7 @@ class UserCreateView(
         #     return self.form_invalid(form)
 
         email = form.cleaned_data["email"]
-        if models.Staff.objects.filter(dealer=dealer,user__email=email).exists() or models.Dealer.objects.filter(user__email=email).exists():
+        if models.Staff.objects.filter(user__email=email).exists() or models.Dealer.objects.filter(user__email=email).exists():
             messages.error(
                 self.request,
                 _(