Legal analysis: rolling interest is a folk saying, which is legally called compound interest. Whether private lending can be calculated by compound interest has not been clearly stipulated in our laws. So far, the law has not affirmed or prohibited it. According to the principle of "freedom without prohibition" in civil law, compound interest can be calculated under certain conditions: (1) is a real agreement between the two parties, and (2) does not exceed the maximum interest allowed by law. Article 6 of the Supreme People's Court's Opinions on People's Courts Handling Loan Cases stipulates: "The interest rate of private lending can be higher than that of banks. The local people's court may conduct special management according to the actual situation. Area, but the maximum shall not exceed the bank. Four times the interest rate of similar loans (including interest rate). Beyond this limit, excess interest is not protected. It can be seen that the calculation of compound interest must be within "four times the interest rate of similar loans of banks", otherwise it will be invalid.

Legal basis: Article 26 of the Provisions of the Supreme People's Court on Several Issues Concerning the Application of Laws in the Trial of Private Lending Cases stipulates that the people's court shall support the interest rate agreed by both lenders and borrowers if it does not exceed 24% per annum. 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 28 of the Supreme People's Court's Provisions on Several Issues Concerning the Application of Laws in the Trial of Private Lending Cases stipulates that both borrowers and borrowers shall, after settling the principal and interest of the previous loan, include the interest in the principal of the later loan and reissue the creditor's rights certificate. If the previous interest rate does not exceed the annual interest rate of 24%, the amount stated in the reissued creditor's rights certificate can be confirmed as the later loan principal, and the interest exceeding the part cannot be included in the later 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. According to the calculation in the preceding paragraph, the sum of the principal and interest payable by the borrower after the expiration of the loan term cannot exceed the sum of the initial loan principal and the interest of the whole loan term calculated at the annual interest rate of 24% based on the initial loan principal. If the lender requests the borrower to pay the excess, the people's court will not support it. Article 29 of the Supreme People's Court's Provisions on Several Issues Concerning the Application of Laws in the Trial of Private Lending Cases stipulates that if both borrowers and lenders have an agreement on overdue interest rates, such agreement shall prevail, but the annual interest rate shall not exceed 24%. If the overdue interest rate is not agreed or clearly agreed, the people's court may handle it according to different circumstances: (1) If neither the interest rate during the loan period nor the overdue interest rate is agreed, the people's court shall support the lender's claim that the borrower should pay the interest during the loan period at the annual interest rate of 6% from the date of overdue repayment; (2) If the interest rate within the loan term is agreed, but the overdue interest rate is not agreed, the lender claims that the borrower shall pay the interest within the loan term according to the interest rate from the date of overdue repayment.