65 ILCS 5/8-1-10
Interest received by a municipality upon deposits of money derived from special assessments or special taxes and that part of the interest, penalties, and costs received on account of any delinquent special assessment or special tax, which is in excess of 6% annually on the amount of that delinquent special assessment or special tax from the date of the first voucher issued on account of work done to the date of the receipt of the interest, penalties, and costs by the municipality, shall be used first for paying any expense of the municipality in connection with the collection or withdrawal from collection of any delinquent special assessment or special tax or the preservation of the lien thereof, or in connection with the sale or forfeiture of any real estate for delinquent special assessments or special taxes, or in the preservation of the lien of any certificate of sale or tax deed, and secondly shall be used to pay any warrant, for which there are not sufficient funds, for the payment of past due principal or interest on vouchers and bonds issued in anticipation of the collection of the special assessments or special taxes identified by such warrant.
65 ILCS 5/8-1-10