Technically, if you guys don't sign, the store should refuse to accept the card as per the credit card company's rules. Even if you write C.I.D., See I.D., Ask for I.D., ect on the card, the cashier is supposed to refuse the card for one that is signed or another form of payment.........like cash or check, if checks are still taken at said establishments. I've signed my C.C. then added See I.D. next to the signature, but have yet to be asked for my license when the cashier is the one to swipe it.