Abstract: If money is paid in from a customer, an outstanding amount of a real account of the customer in each of financial institutions is identified, to calculate a shortage between the outstanding amount and a predetermined amount. Whether the money amount paid in from the customer exceeds the shortage is decided and, if the pay-in money amount does not exceed the shortage, the pay-in money amount is determined to be a pay-in money amount for the real account, to perform pay-in processing. If the pay-in money amount exceeds the shortage, the shortage is determined to be a pay-in money amount for the real account. Then, almost the same arithmetic operations are repeated on real accounts other than the real account for which the pay-in money amount has been determined, to determine a pay-in money amount for the real accounts other than that real account, thus performing pay-in processing.