You should say that the primary card and the secondary card share the same account. Now basically every bank's credit card business can handle primary and secondary cards. You can apply for several supplementary cards for each bank card master card, and the number of supplementary cards is limited according to the regulations of the credit card issuing bank. The cardholder of the main card has the right to request cancellation of its supplementary card, and all the transaction funds of the supplementary card, corresponding interest and expenses will be transferred to the account of the main card, and the cardholder of the main card will bear all the repayment responsibilities, but the cardholder of the main card and the cardholder of the supplementary card will be jointly and severally liable for the debts.

If you want to apply for a supplementary credit card, you need to download the supplementary credit card application form from the internet or go to the outlet to collect it. After the cardholder of the primary card and the cardholder of the secondary card fill in the fields of the primary card number and the secondary card number respectively, they should sign the signature fields of the primary card and the secondary card, attach a copy of the ID card of the secondary card holder, and then submit the application form and related materials to the bank staff.