How to find your debit/credit card security code
To help guard against fraud, the major credit card companies have implemented a system to ensure the credit card used in a transaction is actually possessed by the user. This system may be variously called CVV2 (Visa), CVC2 (MasterCard), or CID (American Express, Discover). The verification number is a non-embossed number printed on the credit card.
American Express
For American Express cards, the number is located on the front of your card, on the right hand side above your card number. The number on American Express cards is four digits long.
Visa / Mastercard / Discover
For Visa, Mastercard, and Discover, the number is located on the back of your card, on the right hand side next to you card number. The number for Visa, Mastercard, and Discover is three digits long.