CVV is an anti-fraud security feature to help verify that you are in possession of your credit card.
For Visa / Mastercard, the three-digit CVV number is printed on the signature panel on the back of the card immediately after the card's account number.
For American Express, the four-digit CVV number is printed on the front of the card above the card account number.
|Visa / Mastercard||American Express|
|A 3-digit number in reverse italics on the back of your credit card||A 4-digit number on the front, just above your credit card number|