If the PCT is not associated to a customer number at the time of filing, how can it be done later?

A request to associate a PCT application with a customer number can be sent to the EBC. Please submit form PTO-2248, "Request to Update a PCT Application with a Customer Number." It must be faxed or mailed to the Electronic Business Center. See customer number for further information.

USPTO FAQ - Questions and Answers (15AUG2007)