the main card refers to the bank card that plays a leading role in the use of multiple bank cards under the same account, and the cardholder of the main card must bear all the debts under the sub-card. A secondary card refers to a bank card that is in a subsidiary position in the use of multiple bank cards under the same account. The main card and the auxiliary card * * * use a fund account and credit line, but they can set different transaction passwords. The main card and the supplementary card need to be applied separately. Generally, the application form for supplementary card will be published separately on the credit card application form, and the maximum number of supplementary cards that can be applied for will be stated. The applicant can also complete the application procedures for the main card and the supplementary card at one time. Relationship between the primary card and the secondary card of ABC Credit Card: All debts incurred by the secondary card holder when using the credit card shall be borne by the primary card holder, and the primary card holder shall directly perform the debts to the card issuer or special unit. The primary card and the secondary card belong to the same account, and the credit line is enjoyed. The main cardholder and the deputy cardholder are mostly related to property, or know and trust each other, and there are agreements such as gift, entrustment and paid commitment between them. In the relationship between primary and secondary cardholders, the primary cardholder is in a dominant position, and the primary cardholder has the right to decide to add or cancel secondary cardholders, while the secondary cardholders are in a subordinate position. If the primary card is cancelled, the secondary card should be returned to the card issuer voluntarily. When the cardholder of the primary card requests to stop using the secondary card midway, he should also return the secondary card to the card issuer. If there is an outstanding debt, the debt will still be borne by the main cardholder. The main cardholder has all the rights to supervise, use or stop all the enjoyment items of the deputy cardholder. The main card and the deputy card are closely related, and they are responsible for the danger of arrears caused by the deputy card.