I am interested if other banks have an auto closure process for accounts where a TIN is not obtained within a reasonable time period, as opposed to just blocking the account. If possible, I would like to know who you are regulated by in the answer.

Regulated by the FDIC and recently examined with no issues. 30 days customer receives a warning - 60 days account is closed.

In this case, the CIP must include procedures to confirm that the application was filed before the customer opens the account and to obtain the taxpayer identification number within a reasonable period of time after the account is opened.

Your procedures must require you to obtain the TIN, nothing less. If you don't get it the account should be closed.

The CIP regulation dances around the idea of controlling the customer's use of the account in circumstances where the bank is unable to verify identity. However, it does not suggest the same response is possible when the bank fails to obtain one of the four required pieces of information.