The National Change of Address (NCOA) program makes change-of-address (COA) information available to mailers to help reduce undeliverable or duplicate mail pieces. Input address information provided by a mailer to the NCOA licensee is first standardized to conform to USPS requirements, including the ZIP+4 code. NCOA helps reduce undeliverable-as-addressed mail by correcting input addresses prior to mailing.

The Coding Accuracy Support System (CASS) improves the accuracy of carrier route, five-digit ZIP, ZIP+4, and delivery point codes that appear on mail pieces. CASS enables the Postal Service to evaluate the accuracy of address-matching software programs in three areas: (1) ZIP+4 delivery point coding, (2) carrier route coding, and (3) five-digit coding. CASS Stage I enables businesses with address-matching software to test their software against test addresses provided by the Postal Service.