According to the regulations of China Merchants Bank Credit Card, the minimum repayment amount of China Merchants Bank Credit Card is 10% of the credit card bill amount. This means that when the bill amount of the credit card is 12000 yuan, the minimum repayment amount of the credit card is12000 *10% =1200 yuan.

It should be noted that for bills that have been paid by installments, the minimum repayment amount cannot be made, so the minimum repayment amount needs to be added with the installment bill amount.