A portable card reader 22 reads data from a credit card 20 issued by an account settlement institution, transmits the data for the card and the data for a service charge to the account settlement institution. When the account settlement institution receives from the portable card reader 22 the data for the credit card 20 and the data for the service charge, the account settlement institution issues a credit inquiry for the consumer based on the data received for the credit card and predetermined data for determining the validity of an account settlement card, and settles the service charge based on the result of the credit inquiry obtained by the credit inquiry and the service charge data that is received. Upon receiving the result of the credit inquiry, the portable card reader 22 issues a receipt in accordance with the result of the credit inquiry and the service charge data.