There is no such thing as a "primary" co-owner. Co-owners are equal in ownership, right, and access. If a co-owner dies, ownership of the account legally changes at the moment of death, whether or not the bank addresses the change. Ideally, the change in tax reporting will take place before the end of the year.
That said, you cannot simply drop the decedent's name and change things the day you learn of the death of a co-owner. As efficient as that might be, it is certain to upset the surviving co-owner or a family member in 99% of the cases. I recommend waiting at least a couple of weeks to see if the surviving owner comes in on his or her own to ask for the updates. If no one shows up after 30 days (some would suggest going as long as 60 days), put a carefully-worded request in the mail that the survivor contact you to arrange for the changes to be completed. If year-end is rapidly approaching, you can push it a little more.
John S. Burnett
Fighting for Compliance since 1976
Bankers' Threads User #8