Every person who has the same surname as the chief is deemed to be a member of the clan. Equally a person who offers allegiance to the chief is recognised as a member of the clan unless the chief decides that he will not accept that person's allegiance.
There is no official list of recognised septs. This is a matter for each chief to determine. But where a particular sept has traditionally been associated with a particular clan it would not be appropriate for that name to be treated by another clan chief as one of its septs.