70 ILCS 2405/22a.17
The ordinance provided for in this Act may provide that the aggregate amounts assessed in each individual assessment shall be divided into annual installments not more than 10 in number. Such division shall be made so that all installments shall be equal in amount except that any fractional amount shall be added to the first installment. The first installment together with interest thereon and on the unpaid balance of the assessment shall be due and payable on first January 2nd after the date of the first voucher issued on account of the work, and successive installments and interest shall be due on each January 2nd thereafter until the assessment is paid. The district shall file with the clerk of the circuit court in which such assessment was confirmed a certificate signed by its clerk or assistant clerk of the date of the issuance of the first voucher within 30 days after the issuance thereof. All installments shall bear interest until paid at a rate specified in the ordinance, which shall not exceed the greater of 9% per annum or 125% of the rate for the most recent date shown in the 20 G.O. Bonds Index or average municipal bond yields as published in the most recent edition of The Bond Buyer, published in New York, New York, at the time the ordinance is passed. Interest on assessments shall begin to run from 30 days after the date of the first voucher issued on account of construction work done, and all accrued interest shall be payable with each successive annual installment. In all cases the district's collector, whenever payment is made on any installment, shall collect interest on the entire unpaid balance of the assessment up to the date of such payment whether the payment be made at or after maturity. Any person may at any time pay the whole assessment against any lot, piece or parcel of land or any installment thereof with interest up to the date of the payment.
70 ILCS 2405/22a.17