The CASS (Coding Accuracy Support System) is a USPS (United States Postal Service) process designed to improve the accuracy of your mailings by verifying your address list against an official list of all known deliverable addresses in the United States. The official list is updated quarterly by the USPS.

CASS Certification may include the following fields:

  • Zip plus 4 coding
  • Postal Abbreviations for Street Suffixes (Ave, St, Blvd, Ct)
  • Postal Abbreviations for Cities (Little Mtn, Grand Jct)
  • Postal Abbreviations for Directions (S, SE, N, NE)
  • Placement of secondary address information (Suite/Apt)
  • Non-address information will be stripped from the address. (C/o, Attn: etc)
Note: Not every address is able to be CASS certified. For example, if you live at 101 Main Street, and your next-door neighbor's house is 105 Main Street, an address with 103 Main Street is invalid and CASS certification would reject the address. Any options that we choose on the AddressFinder import wizard will not count against CASS certification (ex: Selecting 'Do not abbreviate address elements according to USPS standards').

Example of expected results:

Before CASS Certification
John Doe
100 Main Street
Apartment 256
Charleston SC, 29406

After CASS Certification

John Doe
100 Main St Apt 256
Charleston SC 29406-6404

For more information, refer to