12 installments of 9,000 yuan with China Merchants Bank Credit Card: Installment fee for each installment = 9,000 × 0.66% = 59.4 yuan. The principal payable in each period is 9000/12=750 yuan. The total repayment required for each period is 809.4 yuan.

China Merchants Bank credit card installment is interest-free, but there is a handling fee. The handling fee for 12 installments of China Merchants Bank credit card is 0.66%. Handling fee per period = total installment amount × handling fee rate per period. The total principal amount of the installment is amortized evenly on a monthly basis, and the remainder is included in the last installment. The installment amount of each installment and the handling fee of each installment are recorded at the same time.

Handling fee

Credit card installment payment refers to a one-time payment from the bank to the merchant for the goods (or services) purchased by the cardholder when the cardholder uses the credit card to make large purchases. The process of spending funds and then having the cardholder repay the bank in installments and pay handling fees. The bank will deduct consumption funds and handling fees from the cardholder's credit card account in installments based on the cardholder's application, and the cardholder will repay according to the monthly credit amount. In the early days of the credit card installment business, banks often promoted it as "interest-free", and indeed many citizens were "fooled". In fact, interest-free is not free, it’s just called something different.

In general, the one-year credit card installment fee is lower than the annual cash withdrawal interest of 18%, and higher than the bank's one-year commercial loan interest of 5.31%. It is worth mentioning that commercial bank loan interest rates have been reduced many times in recent years, but the standards for credit card installment fees and cash withdrawal interest have rarely changed. Although the standards for credit card installment payment fees vary from bank to bank, the calculation method is roughly the same.

Assume that the installment amount is 1,200 yuan, divided into 12 installments, with each installment (month) repayment of 100 yuan, the handling fee is 0.6%/month, and the actual monthly deduction is 101200×0.6%=107.2 Yuan. If other factors are not considered, the convertible nominal annual interest rate is 7.2%. However, the cardholder does not always owe the bank 1,200 yuan. In the last month, he actually only owed the bank 100 yuan, but the bank still charged a handling fee of 1,200 yuan. .

According to calculations, the true annual interest rate paid by cardholders is approximately 15.48%. According to the correct calculation formula, it should be 1200*0.6%*(1+0.6%)^12/((1+0.6%)^12-1)=103.94 yuan, which means an extra 3.2% handling fee will be paid in each period.