Illinois constitution
Article XIV
Section 3

Amendments to Article IV of this Constitution may be proposed by a petition signed by a number of electors equal
in number to at least eight percent of the total votes cast for candidates for Governor in the preceding gubernatorial election. Amendments shall be limited to structural and procedural subjects contained in Article IV. A petition shall contain the text of the proposed amendment and the date of the general election at which the proposed amendment is to be submitted, shall have been signed by the petitioning electors not more than twenty-four months preceding that general election and shall be filed with the Secretary of State at least six months before that general election. The procedure for determining the validity and sufficiency of a petition shall be provided by law. If the petition is valid and sufficient, the proposed amendment shall be submitted to the electors at that general election and shall become effective if approved by either three-fifths of those voting on the amendment or a majority of those voting in the election.