PURPOSE: To automatically calculate and output the amount of difference between the total of tax amounts collected from member customers during a prescribed term and a tax amount corresponding to the total amounts of taxed articles of member customers during the prescribed term.

CONSTITUTION: This device is provided with a member file 6 equipped with accumulation areas for the amounts of taxed articles and tax amounts corresponding to member numbers respectively allocated to member customers, the tax amount corresponding to amounts respectively stored in taxed amount accumulation areas 6a by member numbers in this member file 6 is calculated at suitable timing, the amount of difference is calculated between the calculated tax amount and the amount stored in the taxed amount accumulation area 6a for the relevant member number in the member file 6, and the differential amount is reported out together with the relevant member number.