Ohio Rev. Code § 5711.18
In the case of accounts receivable, the book value thereof less book reserves shall be listed and shall be taken as the true value thereof unless the assessor finds that such net book value is greater or less than the then true value of such accounts receivable in money. In the case of personal property used in business, the book value thereof less book depreciation at such time shall be listed, and such depreciated book value shall be taken as the true value of such property, unless the assessor finds that such depreciated book value is greater or less than the then true value of such property in money. Claim for any deduction from net book value of accounts receivable or depreciated book value of personal property must be made in writing by the taxpayer at the time of making the taxpayer's return; and when such return is made to the county auditor who is required by sections 5711.01 to 5711.36, inclusive, of the Revised Code, to transmit it to the tax commissioner for assessment, the auditor shall, as deputy of the commissioner, investigate such claim and shall enter thereon, or attach thereto, in such form as the commissioner prescribes, the auditor's findings and recommendations with respect thereto; when such return is made to the commissioner, such claim for deduction from depreciated book value of personal property shall be referred to the auditor, as such deputy, of each county in which the property affected thereby is listed for investigation and report.
Any change in the method of determining true value, as prescribed by the tax commissioner on a prospective basis, shall not be admissible in any judicial or administrative action or proceeding as evidence of value with regard to prior years' taxes. Information about the business, property, or transactions of any taxpayer obtained by the commissioner for the purpose of adopting or modifying any such method shall not be subject to discovery or disclosure.
R.C. §5711.18