If you are using a Visa, Mastercard, or Discover card, it is a 3 digit number
that appears to the back right of your card (see below).
If you are using an American Express card, the verification number is a 4
digit number that appears on the front of your card, above and either on the
left or right of the card number (see below)
If your card does not have a verification number, try another card or enter the number 000.