Card Verification Value (CVV) also known as Card Security Code (CSC) or Card Identification Digit (CID) is an additional security feature for web based payments. The “Card Identification Digits” can be either three or four digits in length depending on the card issuer.

For example, Visa, MasterCard, and Diners Club show the CSC or CVV as the three-digit value printed on the signature panel on the back of the card.
 

For American Express, the Security Code is the 4 digit printed (not embossed or raised) number on the left or right of the card, above or below the card number. For BTA or corporate purchasing cards without CVV, please enter any number into the CVV field.