diff --git a/src/sipcentric/__init__.py b/src/sipcentric/__init__.py
index d15ccb8..f01572f 100644
--- a/src/sipcentric/__init__.py
+++ b/src/sipcentric/__init__.py
@@ -378,46 +378,51 @@ class OutgoingCallerId(APIObject):
     TYPE = "outgoingcallerid"
 
 
-class CreditStatus(APIObject):
-    URLPART = "creditstatus"
-    TYPE = "creditstatus"
-
-
-class CustomerPricing(APIObject):
-    URLPART = "pricing"
-    TYPE = "customerpricing"
-
-
-class Limits(APIObject):
-    URLPART = "limits"
-    TYPE = "customerlimits"
-
-
-class CallCharging(APIObject):
-    URLPART = "callcharging"
-    TYPE = "customercallcharging"
-
-
-class Permissions(APIObject):
-    URLPART = "permissions"
-    TYPE = "customerpermissions"
-
-
-class LinkedUser(APIObject):
-    URLPART = "linkedusers"
-    TYPE = "linkeduser"
+class CustomerAPIObject(APIObject):
+    MANDATORY_FIELDS = ()
 
     def create(self, parent, **kwargs):
         if self._data:
             self._data.update(**kwargs)
         else:
             self._data = kwargs
-        for k in ("activateUrl", "email", "recordingAccess", "owner", "enabled"):
+        for k in self.__class__.MANDATORY_FIELDS:
             if k not in self._data:
                 raise ValueError('missing mandatory field "%s"' % k)
         return self._create(parent=parent, data=self._data)
 
 
+class CreditStatus(CustomerAPIObject):
+    URLPART = "creditstatus"
+    TYPE = "creditstatus"
+
+
+class CustomerPricing(CustomerAPIObject):
+    URLPART = "pricing"
+    TYPE = "customerpricing"
+
+
+class Limits(CustomerAPIObject):
+    URLPART = "limits"
+    TYPE = "customerlimits"
+
+
+class CallCharging(CustomerAPIObject):
+    URLPART = "callcharging"
+    TYPE = "customercallcharging"
+
+
+class Permissions(CustomerAPIObject):
+    URLPART = "permissions"
+    TYPE = "customerpermissions"
+
+
+class LinkedUser(CustomerAPIObject):
+    URLPART = "linkedusers"
+    TYPE = "linkeduser"
+    MANDATORY_FIELDS = ("activateUrl", "email", "recordingAccess", "owner", "enabled")
+
+
 class Sms(APIObject):
     URLPART = "sms"
     TYPE = "smsmessage"