65 ILCS 5/5-3-2
All resolutions and motions (1) which create any liability against a city or village, or (2) which provide for the expenditure or appropriation of its money, or (3) to sell any city, village or school property, and all ordinances, passed by the council or board shall be deposited with the city or village clerk. If the mayor approves of them, he shall sign them. Those of which he disapproves he shall return to the council or board, with his written objections, at the next regular meeting of the council or board occurring not less than 5 days after their passage. The mayor or president may disapprove of any one or more sums appropriated in any ordinance, resolution, or motion making an appropriation, and, if so, the remainder shall be effective. However, the mayor or president may disapprove entirely of an ordinance, resolution, or motion making an appropriation. If the mayor or president fails to return any ordinance or any specified resolution or motion with his written objections, within the designated time, it shall become effective despite the absence of his signature.
65 ILCS 5/5-3-2