The Card Security Code (CSC) is a 3-digit security code printed on the back of your Visa, MasterCard or Discover card or a 4-digit security code printed on the front of your American Express card. The number appears on the signature strip after the last four digits of your account number.

The signature strip may contain your entire account number or just the last four digits of your account number. Either way, the CSC will appear after the last four digits of your account number.

The CSC is used to verify that you have possession of the credit card you are attempting to use.