If you pay back the money within the repayment period, you don't need to pay interest, but you need to pay interest after it is overdue.

Legal basis:

Measures for the supervision and administration of credit card business of commercial banks Article 57 The issuing bank shall clearly stipulate in the credit card collection contract (agreement) the specific operating procedures for repaying credit card loans with the relevant assets of the cardholder, and shall not directly offset the credit card receivables with the assets of the cardholder without the authorization of the cardholder. Unless otherwise stipulated by national laws and regulations. When the issuing bank receives the repayment from the cardholder, it will repay all the debts in its credit card account in the following order: if it is overdue for 1-90 days (inclusive), it will repay the interest or expenses first and then the principal; If the overdue period exceeds 9 1 day, the principal shall be repaid first, and then the interest or various expenses shall be repaid.