CASS stands for Coding Accuracy Support System and is used by the United States Postal Service (USPS) to evaluate the accuracy of software that validates and correct US mailing addresses.  

The USPS requires annual testing of our address validation software and requires a 98.5% accuracy rating based on 150,000 difficult addresses provided by USPS to receive CASS certification.  We are proud to say that we have scored above 99% in each of the last 10 years.

You can read more about CASS and the certification process here and directly from the USPS here.