automated process of the U.S. Postal Service that provides change-of-address information to participating mailers who maintain computerized mailing lists. The USPS sends new addresses to the mailers on electronic media, eliminating the cost, time delay, and errors inherent in manual change processing. Mailers participating in the ACS must print an identifying code on their mailing labels to tell the USPS who should receive the change information. They must also print an ancillary service endorsement on the envelope. Mailers must configure their address records to the ACS format. The USPS charges a small fee (currently $0.20) for each new address.