Ohio Revised Code Title I. State Government § 153.13

At the time named in the contract for payment to the person with whom it is made, the owner referred to in section 153.01 or 153.12 of the Revised Code shall approve a full, accurate, and detailed estimate of the various kinds of labor performed and material furnished under the contract, with the amount due for each kind of labor and material and the materials and amount due in the aggregate, which estimate shall be based upon actual measurement of such labor and materials, and shall give the amounts of the preceding estimate, and the amount of labor performed and materials furnished since the last estimate.  When the major portion of the project is substantially completed and occupied, or in use, or otherwise accepted, and there exists no other reason to withhold retainage, the retained percentages held in connection with such portion and interest thereon accrued shall, within thirty days of substantial completion of, occupation of, use of, or acceptance of the project, be paid to the primary contractor, withholding only that amount reasonably necessary to assure final completion of the project.  Any retained funds withheld after substantial completion of, occupation of, use of, or acceptance of the project, and pending final completion of the project, and interest thereon accrued shall be paid to the primary contractor not later than thirty days after the date of final completion of the project.  Nothing in this section shall be construed as a limitation upon the authority of the director of transportation granted in Chapter 5525. of the Revised Code.