You might be puzzled the first time an online vender asks for your credit card security or verification number when you are buying something. This code is easy to find on Visa and MasterCard credit cards. It is a three-digit number located on the back right side of your card, just next to your signature. American Express cards are an exception, as their four-digit security codes are printed on the upper-right portion of the card's front.
Security Code Purpose
The security code is on your card to ensure that the person placing an order has the card in hand. A would-be thief might get your card number and attempt to make an online purchase. Without the security code, though, he won't be able to complete the transaction. By asking you for the code, a merchant protects against fraudulent purchases.
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