About: Postal address verification

Postal address verification (also known as address , address validation, address verification and CASS certification) is the process used to check the validity and deliverability of a physical mailing address. According to the United States Postal Service, an address is valid (or mailable) if it is CASS-certified, meaning that it exists within the comprehensive list of mailable addresses in their Address Management System. This is different from the credit card Address Verification System (AVS), which is the method used by credit card processors to authenticate ownership of a credit card by verifying that the account on the credit card matches the billing address on file. Credit card AVS does not determine deliverability of an address.