A Mailer ID, commonly known as "MID", may be a 9-digit or 6-digit number, depending on the annual mail volume of the mailer.  They are used to identify mail owners or mail preparers.  Mailer IDs are assigned by USPS to each mail owner or mailing agent that requests them.  They are required in Intelligent Mail barcodes, Intelligent Mail tray barcodes, and Intelligent Mail container barcodes.  Mailer IDs are also identified in electronic mailing documentation submitted with Full Service mailings.

Mailer IDs may be requested through the Business Customer Gateway or by speaking with your local USPS customer service.  For more information regarding this process, visit https://gateway.usps.com/eAdmin/view/knowledge?securityId=MID .

IMbs must be unique for 45 days.  The EZ-Flats system has a mechanism that will enable you to add a start and stop number to the system.  If other equipment on-site has the capability to add the start and stop number, the same mailer ID can be used.  If not, an additional Mailer ID must be acquired.