1.   Go to Tools, User Options
2.   Select Records, Miscelleanous and change attribute name format to Constituent ID
3.   Import file should contain:

  •  ImportID of the constituent the attribute is being added to
  •  Attribute Category
  •  Attribute Description - this will be Import ID of the constituent being added to the attribute
4.   On General tab of the import - make sure identifier being used is Import ID (not Constituent ID or NIN)