Abstract: To enable improvement of efficiency in various settlement operations and cost reduction by linking business-to-business transactions with bank transactions. A computer 100 configured to mediate e-commerce transactions between companies executes processing of receiving invoice data addressed to a buyer from a supplier terminal 200, storing the received invoice data in a storage device 101, and transmitting the invoice data to a buyer terminal 300 in response to an acquisition request from the buyer terminal 300. The buyer terminal 300 executes processing of receiving the invoice data from the computer 100, generating payment schedule data by attaching settlement information to the invoice data, and transmitting the generated payment schedule data to the computer 100.