65 ILCS 5/8-3-4
Whenever a municipality is required to levy a tax for the payment of a particular debt, appropriation, or liability of the municipality, the tax for that purpose shall be included in the total amount levied by the corporate authorities, and certified to the county clerk as provided in Section 8-3-1. However, if a municipality has funds arising from any source whatsoever, including allocations received or to be received under the Motor Fuel Tax Law, as heretofore and hereafter amended which may lawfully be used for the retirement of a particular debt, appropriation or liability of the municipality, or the payment of the next maturing installment thereof, then if the municipality by resolution directs the application of such funds to the payment of the particular debt, appropriation or liability or next maturing installment thereof, it shall certify such resolution to the county clerk as provided in Section 8-3-1. The county clerk shall abate the levy for the payment of the particular debt, appropriation or liability or the next maturing installment thereof to the extent of the funds so certified as available for such payment. The corporate authorities shall determine, in the ordinance making that levy, what proportion of that total amount shall be applied to the payment of the particular debt, appropriation or liability. The municipal treasurer shall set apart that proportion of the tax, collected and paid to him, for the payment of the particular debt, appropriation or liability, and shall not disburse that proportion of the tax for any other purpose until the debt, appropriation or liability has been discharged.
65 ILCS 5/8-3-4