Legal analysis: according to the contract. How to calculate the interest of prepayment can be divided into two types, one is full prepayment and the other is partial prepayment. Full prepayment refers to one-time settlement of mortgage principal and interest. After all prepayment, the interest will be calculated from the day when the principal and interest of the bank are paid off. In other words, as long as you borrow from the bank, the interest will be calculated. Partial prepayment means that only a part of the loan principal and interest is repaid, and the remaining principal and interest are not settled. The outstanding loan principal and interest shall be executed according to the loan interest rate agreed in the original loan contract (continued preferential treatment with discount). There are two repayment methods to choose from for the part of the outstanding loan balance repaid in advance. One is to shorten the repayment cycle, and the monthly payment is inconvenient; Second, the repayment period remains unchanged, reducing the monthly payment. In contrast, the first one can save more interest.

Legal basis: Provisions of the Supreme People's Court on Several Issues Concerning the Application of Law in the Trial of Private Lending Cases.

Article 26 If the interest rate agreed between the borrower and the lender does not exceed the annual interest rate of 24%, and the lender requests the borrower to pay interest at the agreed interest rate, the people's court shall support it. The interest rate agreed between the borrower and the borrower exceeds the annual interest rate of 36%, and the interest agreement in excess is invalid. The people's court shall support the borrower's request to the lender to return the part of the interest paid that exceeds 36% per annum.

Article 27. The loan amount specified in debt certificates such as IOUs, receipts and IOUs is generally recognized as the principal. If interest is deducted from the principal in advance, the people's court shall confirm the actual amount lent as the principal.

Article 28 After both borrowers and borrowers settle the principal and interest of the previous loan, they will include the interest in the principal of the latter loan and issue a new certificate of creditor's rights. If the previous interest rate does not exceed the annual interest rate of 24%, the amount specified in the reissued creditor's rights certificate can be confirmed as the later loan principal. Excess interest cannot be included in the future loan principal. If the agreed interest rate exceeds the annual interest rate of 24%, and the parties claim that the excess interest cannot be included in the later loan principal, the people's court shall support it.