What is the Card Security Code?
The Card Security Code is an important security feature for credit card transactions on the Internet, over the phone, or in any situation where the card is not present. This code will have 3 or 4 digits and will be in a different location depending on the card type. Requiring this code to be entered adds another layer of security to a transaction.
The CSC check makes sure that the number has the correct format and number of digits for the card type being used, and also compares the CSC to the card on record.