Sales data processing system capable of automatically calculating sales taxes

摘要

A sales data processing system wherein an upper limit value, a lower limit value, and a tax amount are entered into a tax amount list. The upper limit value and the lower limit value define a predetermined range of sales amounts, and the tax amount is determined based on a sales amount defined within the predetermined range. Difference values are calculated between a presently entered one of the upper and lower limit values and a previously entered one of the upper and lower limit values, and the calculated difference values are stored in accordance with a calculation order. A first difference value series not having regularity is judged, and a second difference value series having regularity repeated in a predetermined pattern from a series of the stored difference values is also judged. A tax amount information table is formed which has a tax amount information pattern in which the first difference value series not having regularity is used as a non-cyclic portion and a first cycle of the second difference value series having regularity is used as a cyclic portion.