65 ILCS 5/9-1-8
Unless a claim is made by the person entitled thereto before the passage of an ordinance by a municipality, as specified in Section 9-1-6, all interest therein and all right and title thereto of all claimants shall be forfeited and barred. No action shall be begun or claim made for any money undistributed or unclaimed as a rebate or refund, received from the making of any local improvement, paid for wholly or in part by special assessment or special taxation, after the money has remained in the possession of a municipality undistributed or unclaimed as a rebate or refund, for a period of 4 years or more from the due date of the last installment, and where the money has been set aside and transferred into the unclaimed rebate fund in the manner provided in Sections 9-1-5 through 9-1-7.
65 ILCS 5/9-1-8