To apply for a supplementary card of a credit card, the main cardholder and the supplementary card applicant need to handle it together, and the relevant information of the supplementary card user needs to be provided when handling it, which can generally be handled through online application or filling in an application form.

If the credit card master card has not been processed, the customer can check the application for supplementary card at the same time when applying for the master card, and fill in the application information of the master card and supplementary card according to the requirements on the credit card application form. At the same time, the holders of the primary card and the secondary card must personally sign, and attach the financial certificate, permanent residence certificate, identity certificate and other materials of the primary card holder, as well as a copy of the ID card of the secondary card holder and the applicant relationship certificate of the primary card and the secondary card, so that the primary card and the secondary card can apply together.

If the credit card master card has been processed, the master cardholder can fill in the application form for the supplementary card of the credit card separately, and attach a copy of the ID card of the supplementary card holder and a certificate of the relationship between the master cardholder and the supplementary card holder. At the same time, the main cardholder must personally sign and provide the main card number and other related information on the application form for application.