The CVC control number is a three-digit number, typically the last three digits in a row and they are printed on the back of all VISA, Eurocard, MasterCards and Diners cards (not American Express).
You can find your four-digit card verification number on the front of your American Express credit card above the credit card number on either the right or the left side of your credit card.
For American Express credit cards issued in Croatia, starting with number "3775", there is a three digit control number on the back of the credit card.
