The "last three digits code" is the last three digits located at the signature on the back of the credit card, also known as CVV or CVC code, which is generated by the coding rules and encryption algorithm of the issuing bank. Generally speaking, these three numbers are unique and are used to identify individuals. Generally, it is impossible to pay for an input error. In the payment process, if the merchant provides the "last three codes" to the bank, the bank will obtain the authorization of the cardholder to the merchant by default, thus allowing the transaction.