When a customer terminates their Private Mail Box (PMB), the Commercial Mail Receiving Agency (CMRA) may, but is not required to, notify the Post Office immediately. It is, however, required that the CMRA provides the USPS with a quarterly report of customers who have terminated their relationships with the CMRA. This allows us to adequately monitor CMRA compliance and to determine potential fraudulent activity. Annual submission of the updated list of CMRA customers is inadequate because the average customer turnover numbers at CMRAs are significant and recurrent.

Source USPS