OneCode ACS®

OneCode ACS allows customers mailing First-Class Mail®, Standard Mail®, or Periodicals (flats or letters) to receive electronic or automated address corrections through the use of the Intelligent Mail® barcode (IMb). Technical information required to produce the Intelligent Mail barcode can be found at

Information embedded in the IMb includes the Mailer ID, which is used to identify the mail owner or mail service provider. The Sequence Number can be used to trace back to the customer, or it can be used to identify the mailpiece itself. The Service Type Identifier in the IMb represents the ancillary service requested, and on First Class Mail it can replace the printed endorsement (Standard Mail still requires a printed endorsement).

Use of the IMb allows for a less ‘cluttered’ address block (as illustrated below in Exhibit 1) on your mailpiece, and when used on letters may provide automated notices and lower address correction fees.

Exhibit 1: OneCode ACS Mailpiece

Exhibit 1Exhibit 1: OneCode ACS Mailpiece


  1. The Intelligent Mail barcode applied to the mail contains the following information:
    1. Presort information (flats only)
    2. Service Type Identifier that requests specific services like ACS™ and/or Confirm®
    3. Mailer ID that identifies the mail owner or mail service provider
    4. Serial or sequence number that uniquely identifies the mailpiece or the addressee
    5. Routing information that provides the ZIP Code™ and delivery point validation that allows the mail to be sorted directly to the address

Note: The optional printed Ancillary Service Endorsement (not shown) provides the Postal Service™ with the sender's instructions on how to handle the mail if it is UAA. When using the IMb on First Class Mail, the printed endorsement is optional. On Standard Mail, the printed endorsement is still required.

Technical information on OneCode ACS can be found at: