The card security code is a unique three or four-digit number printed on your debit/credit card. The number is not embossed on the card so that it cannot be printed on receipts - making it difficult for anyone other than the genuine cardholder to know it.

Visa, Mastercard, and Discover, use the last three-digit number printed on the reverse of the card.

American Express cards have a four-digit number printed on the front of the card, above the account number.