Visa | Card Verification Value (CVV2) | Three digits to the right of the credit card number in the signature area on back of the card. |
MasterCard | Card Verification Code (CVC2) | Three digits to the right of the credit card number in the signature area on back of the card. |
American Express | Card Identification Number (CID) | Four digits printed (not embossed) on the right front of the card above the credit card number. |