The credit card check code refers to the last three digits of a string of numbers under the small white bar on the back of the credit card. Credit card verification code is generally used to verify the identity of credit card users. Credit card check code is also called credit card security code.
On the back of each credit card, the last three digits of the two sets of numbers displayed in italics at the end of the signature are the credit card verification code. These three digits are generated by the card number, expiration date and service constraint code of the credit card, and by the coding rules and encryption algorithm of the issuing bank.