At least 3 days. The grace period for Japan Post Bank credit cards is four days. According to Article 14 of the "China Bank Card Industry Self-Discipline Convention", the Postal Savings Bank provides cardholders with "time-tolerant services" and should provide cardholders with a certain period of repayment grace period services. At least 3 days from the due date of repayment, when the cardholder repays the loan within the repayment grace period, it shall be regarded as the cardholder repaying the loan on time. If you repay beyond the grace period, the overdue repayment record will be reported to the central bank for credit reporting. Overdue payment will not only incur late fees and interest, but will also lead to a credit check by the central bank, which will have a negative impact on future loans to buy a house or a car, so you must repay in time.