Bank of China’s supplementary card (also called supplementary card) can be repaid directly. It should be noted that the supplementary card of Bank of China's BOC series credit card has a balance in arrears, which needs to be repaid to the supplementary card and cannot be repaid to the main card. Because the main card and supplementary card of this type of card are not in the same account, they need to be repaid separately. The supplementary card of Bank of China's Great Wall series of credit cards is in the same account as the main card. The supplementary card can be repaid directly to the main card or to the supplementary card.