Refers to the difference between the new accounts payable and the original accounts payable caused by the change of the unit price of the goods in the actual settlement after the enterprise purchases the goods from the supplier in the normal business activities. The price difference refers to the futures price difference of different grades, different delivery months, different commodities and different delivery locations. It also refers to the price difference of the same commodity due to various conditions, such as wholesale and retail price difference, regional price difference and seasonal price difference. The difference between buying and selling goods is the main part of some businessmen's profits.