The Credit Card Validation Code is a 3 or 4 digit security code printed on the card. This number is printed on your MasterCard & Visa cards in the signature area of the back of the card. (it is the last 3 digits AFTER the credit card number in the signature area of the card). On American Express cards, this number appears on the front of the card following the credit card number (it appears as 4 smaller digits, AFTER and to the upper right of the credit card number).