Card/ Verification code (CVC2)
This field is used in assigning a value that assists in authenticating the physical presence of a Visa or MasterCard credit card. Card Verification is not contained in the magnetic stripe information nor does it appear on sales receipts; it is an additional 3 to 4-character value, printed on the front or back of Visa and MasterCard cards. This field is used to support the following card verification programs.

o Visa - Card Verification Value 2
o MasterCard - Card Validation Code 2
 
VISA - Back of Card
Visa - has three (3) numbers
Master Card - Back of Card
MasterCard has three (3) numbers

Credit card (Visa, Amex & Master) companies routinely request the identification number on the back of the card. This is an added security procedure to protect the card owner
Always provide this ID number for your protection
and to prevent long authorization delays