Address verification service (AVS) is a card-network check that compares the billing address a customer types at checkout with the address the card issuer holds, returning a one-letter result alongside the authorization response. Most implementations compare only the house number and postal code, inside the authorization request. Built for mail and telephone orders, it now runs on card-not-present transactions and is widely supported by issuers in the United States, Canada and the United Kingdom. The issuer rarely declines on a mismatch; the merchant decides what codes such as Y, A, Z or N are worth. Blocking no-check codes U, R and S rejects most foreign cards, and a clean match shifts no chargeback liability.
What is address verification service
AVS was built for mail and telephone order sales, where the merchant never sees the card, and became a default check on every card-not-present transaction. At a physical terminal the chip already verifies the card, so no address is collected. Issuers in the United States, Canada and the United Kingdom support AVS widely; many issuers elsewhere do not check addresses at all.
AVS payment verification step by step
Most implementations compare only two data points: the house number and the postal code. A customer entering "221B Baker Street, NW1 6XE" is checked on "221" and "NW16XE", while the street name and city are ignored. The data rides inside the authorization request, so AVS payment verification adds no separate call or latency.
The issuer rarely declines because an address fails. It approves or declines on its own criteria and reports the AVS result as information, leaving the decision on a mismatch to the merchant or to rules in its payment gateway.
What is an AVS code
The address verification service (AVS) code is that single character in the response, carried in a field separate from the approval or decline. Some gateways translate it into labels such as "match" or "partial", so the raw letter may only show up in API responses and reports.
AVS response codes explained
The common letters in Visa and Mastercard US-style processing:
- Y: street address and 5-digit ZIP both match.
- A: street matches, postal code does not.
- Z: 5-digit ZIP matches, street does not.
- N: neither matches.
- U, R, S: no check happened (address unavailable, issuer system down, AVS not supported).
Non-US cards produce other letters: M usually means street and postcode matched, and G marks a non-US issuer that does not participate. Meanings vary by network and processor, so merchants work from their own acquirer's code table.
What do AVS codes mean for a fraud decision
A code is a signal, not a verdict. A Z on a $35 order shipping to the billing address is usually a customer who abbreviated the street. The same Z on a $2,400 order going to a freight forwarder deserves a manual review, and N combined with a new account and an IP address in another country is a strong fraud pattern.
Blocking U, R and S automatically rejects most cards issued outside the US, UK and Canada, so international merchants exempt them or send those payments through 3-D Secure. That matters twice, because a clean AVS match, unlike 3DS authentication, does not shift fraud chargeback liability to the issuer. Stolen card records often include the billing address, which is why rules pairing the letter with a CVV check, order value and shipping destination catch more fraud and decline fewer good customers than AVS alone.