To make the link settlement of a group enterprise as accurate as single settlement.

A computer network having a data base 8 is constructed between each company A and B constituting a group enterprise. An A company prepares claim data capable of the input and display of transaction data 7 having contents sufficient for specifying commercial transaction, stores the transaction data 7 in a data base 8, and transmits the transaction data 1 to a B company in a state that the transaction data 7 can be displayed. Then, transmission/reception date is added to the transaction data 7. The B company confirms the transaction data 7 through the received claim data 1, prepares payment data indicating the end of processing, and transmits the payment data to the A company. Then, the transmission and reception date is added to the transmission data 7. Thus, when it is judged that the commercial transaction in which the transmission and reception date of the payment data is present is validly established, the commercial transaction established until a specific date in the group enterprise can be individually offset.