The applicant for the supplementary card must have lineal relatives with the cardholder of the main card, such as parents, spouses and children, and must also meet the conditions of a natural person with full capacity for civil conduct or a natural person with limited capacity for civil conduct over 13 years old. When the applicant for the secondary card is a minor (18 years old or younger), the legal representative must agree when applying for the secondary card of the credit card in the bank.

There are the following differences between the main card and the auxiliary card:

Annual fee is different: the annual fee of the supplementary card is lower than that of the main card, and generally half of the annual fee of the main card will be charged.

Different status: the main card belongs to the account holder, so it must have the decision right to change and cancel the account, and also have absolute management right to the auxiliary card. The cardholder of the main credit card can apply for multiple supplementary cards from the bank or change the cardholder of the supplementary card, but the cardholder of the supplementary card cannot apply for the supplementary card of the main card or change the cardholder information. The cardholder of the primary card can set the limit of the secondary card. When the cardholder cancels the account of the primary card, the secondary card will not be used. When the primary cardholder cancels the secondary card, the secondary card cannot be used any more. If there is still outstanding debt in the secondary card, it will be fully repaid by the cardholder of the primary card. The loss of the main card or the auxiliary card does not affect the consumption and use of the other card. In addition, some banks have restrictions on the online banking function of the secondary card, and the holders of the secondary card can make online payments, but they can't log in to online banking, view personal consumption records and other related information.

Different lines: both the main card and the auxiliary card have consumption functions, and the overdraft line of the auxiliary card is lower than that of the main card. The credit limit of the main card and the auxiliary card is the same. When the overdraft limit of the main card has reached the upper limit, the secondary card cannot continue to consume, and the cumulative overdraft limit of the main card and the secondary card cannot exceed the maximum overdraft limit of the main card, so the secondary card cannot consume, and the cumulative credit card limit of the two cards cannot exceed the maximum limit of the card.

Repayment is different: the relationship between the main card and the auxiliary card is to share a bank account and enjoy the same consumption rights, so all debts need to be returned to the account when repaying. At the time of repayment, the cardholder of the main card can pay off all debts, and the cardholder of the auxiliary card can also voluntarily return the amount owed by the auxiliary card, but the auxiliary card cannot return the amount owed by the main card. When the secondary card has an overdue record, it will be recorded in the account information of the main card holder. Most banks will print out the bills of the main card and the auxiliary card of the credit card and send them to the main card holder.