Credit card AVS does not determine deliverability of an address.Before an address can be certified as deliverable (CASS-certified), it must first be standardized.This among the other problems you're having is grounds to look for a better solution -- if I was you. I'll let you do your own research, but of course I would suggest one that I've worked on called Live Address.
Obviously this service has nothing to do directly with shipping, as it simply calculates tax based on a user's address (technically, the Zip 4, which is returned by the USPS lookup).There's always a good explanation for why addresses don't validate properly, though each case is different.Our industry-leading Get Best Matches operation, now combines Delivery Point Validation (DPV), Suite Link and Residential Delivery Indicator (RDI) into one robust API call to our USPS CASS Certified™ database engine.) is the process used to check the validity and deliverability of a physical mailing address.In addition, if you’ve only included a five-digit ZIP code, the software will append the correct zip plus 4 so that your address matches the nine-digit ZIP 4 format.
CASS-certified address cleansing and verification software will check your shipping address against the USPS database before printing your shipping label.If there is a needed correction, the software will suggest the USPS-approved address.Our USPS CASS Certified™ address validation service improves internal mail processes and delivery rates by standardizing contact records against USPS data and flagging for vacancy, addresses returning mail, and general delivery addresses.The following methods are used to achieve the most accurate address possible: Because a misspelling usually results in an undeliverable address, commonly misspelled words are corrected. Due to the large number of possible misspellings, not all of them can be accurately detected and corrected.Many cities have several different, commonly used names.Correct addresses also mean less returned mail and a greater ability to make accurate business decisions.