PURPOSE: To quickly detect inequality of data between a terminal equipment and a center device by demanding the inquiry of customer's own total sales data stored in the center device and outputting a compared result between an inquired result and total sales data.

CONSTITUTION: The center device 30 receiving transmitting data collates sales data in the transmitting data with an identification(ID) number, an account balance, a returning condition, etc., stored in its own card data file 32 and determines whether selling is to be recognized or not. Sales data and its result are added to a sales data file 33 to update the contents of the file 33 based upon the determined result and a recognition result is transmitted to the terminal equipment 20. Then, total data in the transmitting data are collated with the data of the terminal equipment, the number of events and a total amount stored in a total data file 34 and comparing both the total data. When both the total data are equal to each other, the total data are updated and an end telegraphic message is transmitted to end the processing. When equality is not obtained, the reason of inequality and the total data of the center device are transmitted to the terminal equipment as an additional telegraphic message.