- Mar 2007
"Technically, a MasterCard is not valid unless signed by the authorized cardholder. If a person has not signed his card, the merchant technically should not complete the transaction." The merchant can only complete the transaction on an unsigned card if the cardholder signs the card in front of the employee and then produces valid identification proving their identity, Monteiro says. The cardholder then has nothing to gain by refusing to write anything but his signature on the signature panel.
Read more: http://www.creditcards.com/credit...z2LvpeFfx6