It is an object of the present invention to enable a buyer to collectively manage information related to a variety of commercial transactions performed by the buyer as well as to the settlements for these transactions. The calendar server 25 supplies a calendar screen to a buyer system 3 that is used by the buyer 1. This calendar screen has electronic invoices addressed to the buyer 1, which are issued by the supplier system 7, and electronic deposit/withdrawal detailed statement of the buyer's deposit account, which are issued by a banking system 13, pasted in the spaces for the relevant dates. When the buyer 1 selects an arbitrary invoice on this calendar screen and inputs his or her approval of this invoice, an account transfer telegraphic message for payment of this invoice is automatically sent to the banking system 13. The calendar server 25 manages the status of each invoice (“opened”, “payment request in progress”, “paid”), and notifies the supplier system 7 and banking system 13 of this invoice status. The calendar server 25 also supplements news such as advertisements which are sent by the supplier system 7 and banking system 13, and so forth, selects news following the buyer's consumption trends, and pastes this news in the spaces on the calendar screen which pertain to dates that slightly precede dates on which buyer consumption other forms without departing from the spirit of the present invention.