Penalty or interest on unpaid taxes.

Cities which act under special charters and which levy and collect their own taxes shall not collect any further penalty or interest on general taxes remaining unpaid four years or more after March 31 of the year for which such general taxes are levied. [S13, §1056-a4; C24, 27, 31, 35, 39, § 6896; C46, 50, 54, 58, 62, 66, 71, 73, 75, 77, 79, 81, §420.248 ]