There are two verification system for the credit card. That is AVS and CVM.
AVS stands for Address Verification System. AVS is only available for the U.S. and partially available in four European countries. In the US, AVS checks if the cardholder's address and zip code matches the information at the card-issuing bank. AVS only uses the zip code and numeric portion of the billing street address. There are many reasons why AVS may fail (recent address change, AVS computers down, etc.). If the address verification fails on any level, the merchant may decline the transaction. If the AVS fails for any reason, the merchant should contact the customer for additional information (for example, the name of the issuing bank, the bank's toll-free telephone number, etc.).
The code will tell you whether or not the address given in the order actually matches that of the cardholder. On some system, the AVS code is comprised of three numbers. The first corresponds to the numbers in the street address. The second corresponds to the zip code. And the third is an overall verification of both. For example, an AVS code of YYY means: "yes" the address matches, "yes" the zip code matches and "yes," both the address and zip code match the cardholder's. But an AVS response code of NYZ means "no" the address does not match, "yes" the zip code matches and only the "zip" code matches.
Don't be fooled by YYY response codes. Some crooks have access to the cardholder's address information. Be observant and know what red flags to look for. Pay close attention to: the product ordered and order size; the e-mail address given; the ship-to address and shipping method requested among other things. Be suspicious of sizeable purchases that are being shipped to a different address, especially if express shipping is requested. Pay attention to whether or not the e-mail address given is valid. If the e-mail address is a person's name, check to see if it matches the cardholder's name. These, among other things, are all red flags to look for.
Below is the common AVS response code letters and their meanings :
Y_____ Exact Match
N_____ Not A Match
A_____ Address Match Only
Z_____ Zip Code Match Only
S_____ Service Not Supported (often for non-US credit cards, get proof from cardholder via fax if possible)
U_____ Address Information Not Available (call cardholder's issuing bank)
X_____ When with "YY" means exact match. Otherwise, "XXU" means address Information Not Available (call cardholder's issuing bank)
R_____ Retry - System Unavailable Or Timed Out
W_____ Zip Code OK
E_____ Error Response For Merchant Service Category Code
CVM stands for Card Verification Methods (VISA = CVV2, MasterCard = CVC2, and American Express = CID use a security code of 3 or 4 extra digits imprinted on the card, but not embedded or encrypted in the magnetic stripe. This verification code does not appear on credit card receipts. Since most fraudulent transactions result from stolen card numbers rather than the actual theft of the card, a customer that supplies this number is much more likely to be in possession of the credit card. VISA claims that the use of AVS with CVV2 validation for card-not-present transactions can reduce chargebacks by as much as 26%.