(2) Notice of all assessments levied by a district shall be given to the landowner by mail and shall be payable on the 30th day after such notice is mailed. All assessments paid after the due date shall be charged interest at the rate of not more than 12 percent per annum. All assessments shall be paid to the secretary-treasurer of the district and a receipt shall be issued therefor. From time to time the board shall order the satisfaction of the liens against lands on which assessments have been paid, and a copy of such order shall be filed with the county clerk of the county in which the lands are located. [Amended by 1961 c.186 §9; 1981 c.122 §1]