Collect the proof materials of interest repayment by yourself, prove that you have paid the interest, and ensure the trouble of unclear interest. If the user borrows money for a friend, but the loan contract is signed with the lending institution, then the loan interest needs to be returned by the user himself. As the authorized person, the user helps a friend to handle the loan business. The loan contract is signed by a friend and a lending institution, and the loan interest is returned by the friend at this time.