Every shop has a different limit for the amount of money you can spend on a card in the shop without it being checked first with the issuer. When you buy things, which are more than this limit, the sale has to have the card issuer's authorization. This can either be done by telephone or electronically when the card is swiped through the till by the shop assistant. In this way, stolen cards are caught and cardholders are stopped from going over their credit limit. Sometimes to authorize the transaction, the issuer needs to check the cardholder's identity.
