Ohio Rev. Code § 5715.16: County board of revision to make necessary corrections in assessments.

On the second Monday of May, annually, the county auditor shall lay before the county board of revision and the tax commissioner the returns of the auditor's assessment of real property for the current year, and such board shall forthwith proceed to revise the assessment and returns of such real property. If the board finds that any tract, lot, or parcel of land, or any buildings, structures, or improvements thereon, or any minerals therein, or rights thereto have been improperly listed either as to the name of the owner or the description or quantity thereof, or have been incorrectly valued, or have been omitted and not yet valued, it shall make the necessary corrections and give to each such incorrectly valued or omitted tract, lot, or parcel of land, or any buildings, structures, or improvements thereon, or any minerals therein or rights thereto, their corrected taxable value.

The auditor shall not make up the auditor's tax list and duplicate nor advertise as provided in section 5715.17 of the Revised Code until the board has completed its work under this section and returned to the auditor all the returns laid before it with the revisions thereof.