The Mailer Identifier (MID) is a field within the Intelligent Mail barcode that is used to identify mailers. MIDs are assigned by the USPS® to a Mail Owner, Mailing Agent or other service providers who request them.
MIDs are either a 9-digit or a 6-digit numeric code and are assigned based on annual mail volume criteria. One 9-digit MID is assigned to a business location without a volume requirement.
How to obtain a Mailer ID
To request a Mailer ID (MID) go to http://www.usps.com/ and select the Business Customer Gateway located on the bottom right hand corner of the web page
footer. You must either be an existing or a registered user, or can sign-up as a new user for a business account to gain access to the Business Customer Gateway. Once you have access, request the "Mailer ID" tool and proceed with the "Request a MID" button to obtain a MID.
If you need additional MIDs, not obtainable through the Business Customer Gateway-MID Tool, refer to the Mailer ID Exception Process. Mailing Agents who are authorized to obtain MIDs on behalf of Mail Owners, should refer to the Agent Application Process. All forms can be viewed and printed from the Important Links box on this web page. Complete the Mailer ID Application and the Additional Accounts Information sheet if applicable and submit them to the Business Mail Entry Unit (BMEU) or the Mailpiece Design Analyst for processing.
To locate your local Business Mail Entry Unit (BMEU) or Mailpiece Design Analyst (MDA), go to the following URLs:
www.usps.com/nationalpremieraccounts/findlocators.htm (BMEU locator)
https://ribbs.usps.gov/mda/mda.cfm (MDA look-up tool)
Program Registration Mailer ID Assignment
For shippers who enroll in Shipping Service programs using the Business Customer Gateway, one 9-digit (master) Mailer ID is initially assigned. Subsequent 9-digits are assigned based on a Mail Owner single business or a mail service provider's single-client business shipping location.