Ill. Const. art. VIII, § 2

(a) The Governor shall prepare and submit to the General Assembly, at a time prescribed by law, a State budget for the ensuing fiscal year. The budget shall set forth the estimated balance of funds available for appropriation at the beginning of the fiscal year, the estimated receipts, and a plan for expenditures and obligations during the fiscal year of every department, authority, public corporation and quasi-public corporation of the State, every State college and university, and every other public agency created by the State, but not of units of local government or school districts. The budget shall also set forth the indebtedness and contingent liabilities of the State and such other information as may be required by law. Proposed expenditures shall not exceed funds estimated to be available for the fiscal year as shown in the budget.

(b) The General Assembly by law shall make appropriations for all expenditures of public funds by the State. Appropriations for a fiscal year shall not exceed funds estimated by the General Assembly to be available during that year.