According to Caiti.com's inquiry, the invalid merchant of credit card means that when POS swiping machine signs in or swipes the card, it prompts 03 and 02 invalid merchant response codes, that is, the merchant does not exist in the payment system. Generally, when installing a POS machine, you will first register the payment system with your personal information. After the registration is passed, it will generate its own merchant, including personal ID card information and bank card information. After signing in and downloading the key for the first time, it officially means that the merchant you registered is bound to the POS terminal. In the future, as long as you swipe your card on the bound POS machine, it will be settled in the collection bank card of the bound merchant.