The CASS system improves the accuracy of carrier route, five-digit
ZIP®, ZIP + 4®, and delivery point codes that appear on mailpieces. CASS
is offered to all mailers, service bureaus, and software vendors who
want to evaluate their address-matching software and improve the quality
of their ZIP + 4, CRIS, and five-digit coding accuracy. This process is
graded by the United States Postal Service®, National Customer Support
Center (NCSC), and the results returned to mailers in order to provide
useful diagnostics for correcting deficiencies.