CVV2 Location on VISA, MC and DISCOVER CREDIT CARDS:
The CVV2 three-digit value is printed on the signature panel on the back of Visa, Mastercard and Discover cards immediately following the credit card number.
CID Number Location on AMERICAN EXPRESS cards:
The Card Identification Number is the 4 digit, non-embossed number printed above your credit card number on the face of your card. This number is recorded as an additional security precaution.