Usually, a bank card has a primary card and a secondary card. They share a fund account, but they need to apply separately. At the same time, the main card and the auxiliary card are relatively independent, and different transaction passwords can be set. The secondary card can be said to be a derivative of the main card, which is the capital and credit line of using the main card. Overdraft consumption is ultimately repaid by the main card applicant, so people who use the supplementary card do not need to have proof of financial ability. If your spouse or immediate family member does not meet the requirements for applying for a credit card, or is not old enough to apply for a master card, but needs a credit card, you can apply for a supplementary card on the master card.

The premise of the existence of the secondary card is the existence of the primary card, and the repayment and credit records of the secondary card are recorded on the head of the primary card holder. Therefore, the holder of the main card should pay attention after handling the supplementary card, and must give the card to the client, preferably the spouse or immediate family member.

In addition, because the credit lines of the main card and the auxiliary card are the same, they may not know each other's consumption amount during use. Once the credit limit is exceeded, the merchant needs to ask the issuing bank for temporary over-authorization, which brings inconvenience to consumption.

Therefore, users of the main card and the auxiliary card should communicate frequently to avoid excessive communication. As far as points are concerned, the credit card consumption points of the secondary card will eventually accumulate on the credit card consumption points of the main card.

There is no difference between the use of the secondary card and the main card. The annual fee is generally half of the main card, and you can also enjoy the preferential activities of the bank and the value-added services of the credit card. Some banks may not be able to enjoy the value-added services of individual projects for their Platinum Card supplementary cards. For example, the supplementary card of CITIC Bank does not enjoy the 4-birthday bonus service. The amount of the supplementary card is limited by the cardholder of the main card, which can share the amount of the main card with 100% or a certain proportion of the amount of the main card. Points are usually combined into the main card, but the points of ICBC's secondary card can be used independently.