Three days. Credit card grace period refers to the number of days of repayment grace period. Credit cards have a billing date and a repayment date. After the cardholder consumes the credit card, he needs to repay it on the billing date and repayment date. If the repayment date of the Bank of Communications credit card is 20th of each month, and the Bank of Communications credit card has a three-day grace period, then the repayment deadline is 23rd of each month.