legal ground
Article 675 of the Civil Code
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 overdue interest in accordance with the agreement or relevant state regulations.
Article 677
If the borrower repays the loan in advance, unless otherwise agreed by the parties, the interest shall be calculated according to the actual loan period.
Article 678
The borrower may apply to the lender for extension before the repayment period expires; If the lender agrees, it can be extended.