What is the Credit Card ID asked for?

Where do I find this on my card? Each credit card company — Visa, MasterCard, American Express & Discover — place a special ID number on each card as a means of fraud prevention. When online merchants ask for your Credit Card ID it verifies that the card is in your possession. We ask you for this ID in the interest of the security. Find the ID Number on Your Credit Card For Visa and MasterCard - The credit card ID number on a Visa card is a 3-digit number printed on the signature panel on the back of the card. The ID number always follows the account number. For American Express - The American Express credit card ID number is the 4-digit number printed above your account number on the front of the card. The ID number is not embossed into your card. For Discover - The credit card ID number on a Discover card is a 3-digit number printed on the signature panel on the back of the card. The ID number always follows the account number.  more