System for maintaining continuous total of refund amounts due a customer and for allowing customer designation of the amount of refund to be applied to a purchase

Claim 1

A sales-data-processing apparatus comprising: computing means for computing a potential discount for each customer on the basis of the total price of articles which are purchased by the customer and are eligible for discount; storing means for storing said potential discount or said total price from which said potential discount is calculated for each customer; input means including primary input means for entering customer-identification data for identifying each customer, and secondary input means for entering the discount desired by the customer at the time of calculation; subtraction means for subtracting said desired discount from the total price of the current purchase so as to obtain the final price of the current purchase; display means including primary display means for displaying said potential customer discount according to said customer-identification data entered from said primary input means, and secondary display means for displaying said final price; and updating means for updating said storing means on the basis of said desired discount and said total price of the articles eligible for discount of the current purchase, wherein a remaining discount is obtained by subtracting said desired discount from said potential customer discount in order to obtain a new potential customer discount which is stored in said storing means for use by said customer at the time of a next purchase.