55 ILCS 5/2-6008
All ordinances, resolutions or motions shall be submitted to said board of commissioners in writing, or reduced to writing before any vote shall be taken thereon; and if adopted by the board, the same shall not take effect until after the same shall have been approved in writing by the president of said board, except as hereinafter provided. It shall be the duty of the clerk of said board to deliver to the president thereof, upon his request, the original (or a copy) of each ordinance, resolution or motion, so passed or adopted by said board as aforesaid, within one day after its passage or adoption; and in case the president approves thereof, he shall sign the same, and it shall thereupon be in full force and effect. In case the president shall not approve any such ordinance, resolution or motion, he shall, within five days after the receipt of the same as aforesaid, return it to the clerk of said board, with his objections thereto in writing. Such veto by the president may extend to any one or more items or appropriations contained in any resolution making an appropriation, or to the entire resolution; and in case the veto only extends to a part of such resolution making an appropriation, the residue thereof not embraced within the veto shall take effect and be in force from the time of the receipt by said clerk of such veto of such part. Upon the return of any such ordinance, resolution or motion by the president, with his objections thereto as aforesaid, the vote by which the same was passed shall be reconsidered by the board of commissioners as to so much thereof as may have been vetoed; and if, after such reconsideration, three-fifths of all the members elected to the board shall agree to pass the same by yeas and nays, to be entered on the journal, the same shall take effect, notwithstanding the president may have refused to approve thereof. In case the president shall fail or omit to either sign and approve or return, with his objections as aforesaid, any such ordinance, motion or resolution which shall have been passed or adopted by the board within six days after it shall have been so passed or adopted, the same shall take effect without the approval of the president.
55 ILCS 5/2-6008