In order to receive mail on behalf of your customers, you must be registered and approved by the USPS as a CMRA (Commercial Mail Receiving Agent). The Business Customer Gateway (BCG) is the database used by the USPS to track all approved CMRA accounts and keep record of all customers using mailboxes at those locations. 

As a CMRA, you are responsible for maintaining accurate records of all accounts receiving mail at your address. This includes a USPS 1583 form and the corresponding IDs uploaded to your location’s BGC account.  iPostal1 has created a program to assist you with the upload of this information.  Every quarter, you must certify the Quarterly Report in the BCG, attesting that all the account information is accurate and up to date. 

The Business Customer Gateway can be found on the USPS website. Here is the link to the BCG.