65 ILCS 5/8-2-2
Prior to November 15 of each year, the mayor in municipalities specified in Section 8-2-1 shall submit to the corporate authorities the executive budget for the ensuing fiscal year as prepared by the budget director of the municipality and approved by the mayor. The executive budget, as the same may be revised or altered by the corporate authorities, shall provide the basis upon which the annual appropriation ordinance is prepared and enacted.
The budget document shall set forth estimates, by classes, of all current assets and liabilities of each fund of the municipality, as of the beginning of the fiscal year, for which appropriations are to be made, and the amount of those assets which will be available for appropriation in that year, either for expenditures or charges to be made or incurred during that year or for liabilities unpaid at the beginning thereof. Estimates of taxes to be received from the levies of prior years shall be net, after deducting the amounts estimated to be sufficient to cover the loss and cost of collecting these taxes. These amounts shall include (1) uncollectible taxes, (2) the cost of collecting taxes, (3) the amount of these taxes for the nonpayment of which real estate has been or will be forfeited to the State, and (4) the abatement in the amount of these taxes extended or to be extended upon the collector's books. In order to secure net estimates there also shall be deducted the principal of all unpaid tax anticipation warrants and all interest accrued thereon and an amount estimated to be sufficient to cover all interest to accrue thereon until redemption of these tax anticipation warrants. Estimates of the liabilities of the respective funds shall include (1) all final judgments, including accrued interest thereon, entered against the municipality and unpaid at the beginning of the fiscal year for which the appropriations are made, (2) any amount for which the corporate authorities of the municipality are required to reimburse the working cash fund from the general corporate fund pursuant to the provisions of Division 6 of this Article 8, (3) the taxes levied for the purposes of the reserves provided for in the Illinois Pension Code, as now or hereafter amended and (4) all other liabilities. However, for the purpose of these estimates, judgments, for the payment of which a special tax has been authorized by law, shall not be deemed liabilities of the general corporate fund of the municipality. Also, estimates of taxes to be received from the levies of the years prior to 1945 for general corporate purposes and estimates of the liabilities of the general corporate fund incurred prior to January 1, 1945, shall not be included in the budget document. The budget document shall also set forth detailed estimates of all taxes to be levied for the fiscal year for which the appropriations are to be made, and detailed estimates of all other current revenue to be derived from sources other than such taxes, which will be applicable to expenditures or charges to be made or incurred during that year. All of these estimates shall be so segregated and classified as to funds and in such other manner as to give effect to the requirements of law relating to the respective purposes to which these assets, taxes, and other current revenue are applicable to the end that no expenditure shall be authorized or made for any purpose in excess of funds lawfully available therefor.
65 ILCS 5/8-2-2