As an added security measure, the CVV (Credit Validation Value) is a 3 or 4 digit code embossed or imprinted on the reverse side of Visa, MasterCard and Discover cards and on the front of American Express cards.
On Visa, MasterCard and Discover, you can usually find the CCV number ( 3 or 4 digits) on the back of your credit card, in the signature line area.
On American Express, the 4-digit number (also known as the Card Identification number, or CID) can be found on the front of the card, above your account number.