The card security code (CSC, also called CVV2 by some processors) is a 3- or 4-digit number that is not part of the credit card number. The CSC is typically printed on the back of a credit card (usually in the signature field). The number appears only on the card itself (not on receipts or statements), and thus provides some assurance that the physical card is in the possession of the buyer.

On Mastercard and Visa, the code is usually on the back of the card, to the right of the card number.

On American Express, it is usually on the front of the card, above the card number.