Credit Card Security Number

For VISA and MasterCard:
To find your Credit Card Security Number, flip your card over and look at the signature box. You should see a 16-digit credit card number followed by a special 3-digit code. This 3-digit code is your Credit Card Security Code.

For American Express:
Your credit card security number is a 4-digit code found on the front of your card on the right side above your 15 digit credit card number.