The main card and the auxiliary card share an account with the same function. The debt arising from the transaction of the secondary card is borne by the main card customer, and the interest-bearing rules are the same. Credit card overdraft consumption enjoys an interest-free repayment period of up to 56 days. If the repayment is not made before the due repayment date, an interest of 0.5 ‰ will be charged daily for the amount owed by the credit card from the bank bookkeeping date, and a late fee of 5% will be charged for the unpaid part of the minimum repayment amount. Overdraft cash withdrawal and transfer do not enjoy interest-free repayment period, and 0.5 ‰ overdraft interest is paid from the bank bookkeeping date to the repayment date.