To make a payment with your credit/debit card, we need to know the CVV number from the reverse of the card. This is used by the credit card company to identify you as having the card in your possession when placing the order. Your card will not be authorised and hence your order will be rejected if you do not enter the correct digits.
Depending on the age of the card the CVV number is the 3 or 4 digit number printed on the signature strip on the reverse of the card as shown below.
American Express cards show the card security code (also referred to as the CID number) printed above the imprinted card number on the front of the card (on either the left or right)**.