Visa/Mastercard and Discover Users.
Flip your card over and look at the signature box. You should see either the
entire 16-digit credit card number or just the last four digits followed by a
special 3-digit code. This 3-digit code is your Card Security Code.
American Express Credit Card Users.
Look for the 4-digit code printed on the front of your card just above and to
the right of your main credit card number. This 4-digit code is your Card
Identification Number (CID). The CID is the four-digit code printed just above
the Account Number.
