To manage merchandise inventory so as to be able to sell the inventory without discarding merchandise that expires.

A POS system having a barcode reader for reading a barcode displayed on merchandise is provided. The POS system acquires discount information for discounting the sales price of the merchandise in accordance with the date of manufacture of the merchandise, an expiration date and an elapsed time from the date of manufacture within the term of the expiration date from the barcode read by the barcode reader and calculates a discounted sales price of the merchandise at the present date and hour on the basis of the discount information.