The interest-free period of each bank is different. The 12th is the billing day. For example, CCB sets the 20th day after the billing date as the final repayment date. Then your consumption on September 21st will be credited to your account on October 12th, and 20 days later, November 1st, will be the final repayment date. (Because October has a 31st day). For example, Agricultural Bank of China sets the final repayment date on the 25th day after the bill date. Some banks have a fixed repayment date, such as China Merchants Bank. Regardless of whether it is 28 days in February or 30 or 31 days in other months, the repayment date is fixed. of. You just need to repay according to the repayment date on the bill. Generally, banks will provide paper or electronic bills, or you can also log on to the credit card website to check.