If upon completion of the project it is found that any sum theretofore assessed upon any property is more than sufficient to pay the cost for the public improvement completed, the Council shall ascertain and declare the same by ordinance, and when so declared, it must be entered in the docket of city liens as a credit upon the appropriate assessed owner’s account. If any such assessment has been paid, the person who paid the same or his or her legal representative shall be entitled to a rebate and to the amount of the credit as ascertained and declared.