Legal analysis: it is difficult for creditors to prove the act of claiming rights from debtors before litigation. If it can be proved that the borrower has not repaid the loan after the reminder, the interest can be calculated from the date of reminder. If it is impossible to prove whether the creditor called for a notice before the lawsuit, it shall be regarded as a notice, and the overdue interest shall be calculated from the date of the lawsuit.

Legal basis: Civil Code of People's Republic of China (PRC).

Article 675 The borrower shall repay the loan within the agreed time limit. If the term of the loan is not agreed or clearly agreed, and cannot be determined according to the provisions of Article 510 of this Law, the borrower may return it at any time; The lender may urge the borrower to return it within a reasonable period of time.

Article 676 If the borrower fails to repay the loan within the agreed time limit, it shall pay the overdue interest in accordance with the agreement or the relevant provisions of the state.

Article 677 Where the borrower repays the loan in advance, unless otherwise agreed by the parties, the interest shall be calculated according to the actual loan period.