The Intelligent Mail Barcode is also known as the USPS OneCode Solution or USPS 4-State Customer Barcode (abbreviated 4CB, 4-CB, or USPS4CB). This barcode is adopting a new 4-state 1D barcode that includes more address information than the current code.

An example:

The Intelligent Mail barcode combines information currently found in the PostNet and Planet barcodes. The length of the barcode is fixed at 65 bars. It also contains a CRC-Checksum for verifying the barcode value. There is no error correction. The output of the barcode is a 20, 25, 29 or 31 digit string (0, 5, 9 or 11 digit zip code) containing the following data:

(© USPS-B-3200,Pages 4-5,file:SPUSPS-B3200B001.pdf)

The Mailer ID is a field within the Intelligent Mail barcodes that is used to identify Mail Owners and/or Mailing Agents. The IDs are assigned by the USPS to each Mail Owner and/or Mailing Agent that requests them. A Mailer ID can be a 9-digit field or a 6-digit field. The USPS assigns 6-digit or 9-digit Mailer IDs based upon the mail volume of the mailer. 

• The barcode identifier is a 2 digit field assigned by the USPS. The first digit ranges from 0-9 and the second digit ranges from 0-4.

• Special services include a 3 digit field assigned by the USPS for any special services which range from 000-999.
• The customer identifier is a 6 digit field assigned by the USPS and is unique for each customer. The range is from 000000000-999999999.
• The sequence number is a 9 digit field assigned by the mailer for tracking mail pieces which range from 000000000-999999999.
• The zip code is a 0, 5, 9, or 11 digit zip code which range from none, 00000-99999, 000000000-999999999, 00000000000-99999999999.