The Card Security Code (CSC) appears as the last 3 digits in the back of the credit card and is not part of the Credit Card Number. The CSC is typically in the signature field and typed in reverse italics. Some cards will show the 3 digit CSC code after the credit card's last few numbers and may not always be italicized. See above example (NOTE: American Express card code is located in the FRONT of the card.). We ask for this number because it provides additional assurance that the physical card is in the possession of the owner.