No further appropriations shall be made at any other time within the same fiscal year, unless a proposition to make each additional appropriation has been first sanctioned by a petition signed by electors of the municipality numbering more than 50% of the number of votes cast for the candidate for President at the last preceding general municipal election at which a President was elected, by a petition signed by them, or by a majority of those voting on the question at a general state or municipal election or at a special municipal election duly called therefor. The corporate authorities may by ordinance initiate the submission of the proposition. During any fiscal year the corporate authorities in municipalities subject to this section may adopt a supplemental appropriation ordinance in an amount not in excess of the aggregate of any additional revenue available to the municipality, or estimated to be received by the municipality after the adoption of the annual appropriation ordinance for that fiscal year, or from fund balances available when the annual appropriation ordinance was adopted but that were not appropriated at that time. The provisions of this section prohibiting further appropriations without sanction by petition or election shall not be applicable to the supplemental appropriation for that fiscal year.
(ILCS Ch. 65, Act 5, § 8-2-9)