Carrier Route Codes are unique 9-digit numbers used to identify the more than 600,000 carrier routes used for US Postal Service mail delivery. A carrier route code is made up of the 5-digit ZIP code followed by a letter to designate the type of carrier route and 3 digits identifying a carrier route. Carrier route codes are part of the information matched against USPS databases during Address Correction, Address Verification, and other list enhancement and list hygiene processes.
