Signing means swiping a credit card to make a purchase, and then signing the purchase order printed out by the card machine. This order is in two copies. The merchant keeps one copy here as a stub and the customer leaves one copy here. The purchase order can be kept for a period of time until the bill is verified, or it can be destroyed after a certain period of time. In case of any accounting doubts, if you have a voucher in hand, you can also contact the bank to apply for verification of the merchant's signature.