Ohio Const. art. XVIII, § 9

Amendments to any charter framed and adopted as herein provided may be submitted to the electors of a municipality by a two-thirds vote of the legislative authority thereof, and, upon petitions signed by ten per centum of the electors of the municipality setting forth any such proposed amendment, shall be submitted by such legislative authority. The submission of proposed amendments to the electors shall be governed by the requirements of section 8 as to the submission of the question of choosing a charter commission; and copies of proposed amendments may be mailed to the electors as hereinbefore provided for copies of a proposed charter, or pursuant to laws passed by the General Assembly, notice of proposed amendments may be given by newspaper advertising. If any such amendment is approved by a majority of the electors voting thereon, it shall become a part of the charter of the municipality. A copy of said charter or any amendment thereto shall be certified to the secretary of state, within thirty days after adoption by a referendum vote.