PURPOSE: To reduce the total amount of money after tax by the input reduction amount of money by performing price reduction calculation while considering the input price reduction amount of money includes the reduction amount of money for the amount of a tax.

CONSTITUTION: When the reduced amount is inputted with a reduction key 76, the reduced amount is subtracted from the total amount after tax and the total amount after the reduction is displayed out at a display part 9. Then when registration clearing operation is performed, from the reduced amount is subtracted from the total amount, the difference amount between the tax amounts before and after the reduction amount is subtracted is added, and the tax amount for the total amount after the obtained reduction is made is calculated. Then the tax amount for the total amount after the reduction and the total amount after tax are printed on a receipt together with the reduction amount and difference amount. Consequently, the reduction calculation is performed while the input reduction amount includes the reduction amount for the tax amount, so the total amount after tax is reduced by the input reduction amount.