65 ILCS 55/6
It shall be lawful to provide by the ordinance for any such project, any portion of the cost of which is to be defrayed by special assessment or special taxation, or by ordinance passed at any time before the confirmation of the assessment roll, that the aggregate amount assessed, and each individual assessment be divided into installments not more than ten (10) in number. In all cases such division shall be made so that all installments shall be equal in amount, except that all fractional amounts shall be added to the first installment, so as to leave the remaining installments of the aggregate equal in amount. The first installment shall be due and payable on the second day of January next after the date of the first voucher issued on account of work done, and the second installment one (1) year thereafter, and so on annually until all the installments are paid; and it is the duty of the municipality to file in the office of the clerk of the court in which such assessment was confirmed, a certificate signed by presiding officer, of the date of said first voucher and of the amount thereof, within thirty (30) days after the issuance thereof. All installments shall bear interest as hereinafter provided until paid, at the rate of not to exceed six (6) per centum per annum. Interest on assessments shall begin to run from the date of the first voucher issued on account of work done as aforesaid. The interest on each installment shall be payable as follows: On the second day of January next succeeding the date of the first voucher aforesaid so certified as aforesaid, the interest accrued up to that time on all unpaid installments shall be due and payable and be collected with the installment, and thereafter the interest on all unpaid installments then payable, shall be payable annually and be due and payable at the same time as the installments maturing in such year and be collected therewith. In all cases it shall be the duty of the municipal collectors, as the case may be, whenever payment is made of any installment to collect interest thereon up to the date of such payment whether such 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 as provided herein up to the date of payment.
65 ILCS 55/6