The Card Codes are located as follows.
American Express cards show the 4 digit CVV2 number printed above and to the right of the imprinted card number on the front of the card.	MasterCard CVV2 number is found in the signature area of the back of the card. It is the last 3 digits AFTER the credit card number (if present) in the signature area of the card.	Visa CVV2 number is found in the signature area of the back of the card. It is the last 3 digits AFTER the credit card number (if present) in the signature area of the card.

Why do we use CVV2 Codes.

CVV2/CVC2/CID provides a security feature for "card not present" transactions. It is a three or four digit value which provides your payment processor with a cryptographic check of the card's authenticity. The terms are generally used interchangeably. CVV2 stands for "Card Verification Value 2", CVC2 stands for "Card Validation Code 2", and CID stands for "Card Identification Number". For American Express, the code is a four digit number on the front of the card above the account number. For Visa, Eurocard/MasterCard and Discover the code is a three digit number that appears at the end of the account number(if present) on the back of the card. These code values helps validate two things:

1. The customer has the credit card in his/her possession.
2. The card account is legitimate.