Definicja card verification value

Three or four digits, printed to the right of the credit card account number in the signature panel of a credit card.

This value, contained in the magnetic strip on the back of the card, is a security feature ensuring that the customer has a card and a card account. The card verification value, the account number, and the expiration date form an algorithm during the authorization process. If part of this algorithm is missing or incorrect, the authorization is declined.