Answer:
"Primary" has no meaning in connection with ownership. It is simply the first person listed in the title of a joint bank account.
If the customer wants to change the SSN on which you report interest, there is no specific protocol involved beyond making certain the "new" number is the object of a TIN certification. Note that changing the SSN midyear would cause the interest for the entire year to be reported in the name of the "new" number.
First published on BankersOnline.com 2/18/13