POS code hopping refers to merchant code hopping, which means that when the cardholder swipes the card on the POS machine, the data of merchant category code (MCC) on the purchase order is inconsistent with the data of official backstage merchant code (MCC) of UnionPay, that is, your receipt shows the original merchant, while the backstage of UnionPay shows the merchant with code hopping. The POS machine reads the magnetic stripe information on the cardholder's bank card through the card reader, the POS machine operator inputs the transaction amount, and the cardholder inputs the personal identification information (i.e. password). The POS machine sends the information to the issuing bank system through the UnionPay center to complete the online transaction, give the information of success or failure, and print the corresponding bill.