Ohio Rev. Code § 5719.041
If the payment of a general personal property or classified property tax is not made on or before the last day prescribed by section 5719.03 or 5719.031 of the Revised Code, an interest charge shall begin to accrue and shall continue until all charges are paid, except that no interest charge shall accrue for or in the month in which such payment was due under such section or under the circumstances and for the period described in division (A)(2) of section 5711.33 of the Revised Code or upon delinquent taxes that are the subject of a delinquent tax contract entered into pursuant to section 5719.05 of the Revised Code.
The interest charge shall accrue against the balance of such taxes and any penalty thereon outstanding that remains unpaid on the last day of each month and shall be at the rate per calendar month, rounded to the nearest one-hundredth of one per cent, equal to one-twelfth of the federal short-term rate determined by the tax commissioner under section 5703.47 of the Revised Code for the calendar year that includes the month for which the charge accrues. The charge is payable in addition to the unpaid balance of taxes and penalties on the day the charge accrues, unless the entire balance is sooner paid.
If a delinquent tax contract becomes void, interest shall be charged on the day on which the contract becomes void in the amount that would have been charged had the delinquent tax contract not been entered into and shall thereafter accrue as provided in this section.
Interest shall be allowed, at the same rate per calendar month as is applicable that month for underpayments, on any overpayment of the tax charged on a general personal property or a classified property tax duplicate, from the first day of the month following the date of the overpayment until the last day of the month preceding the date of the refund of the overpayment. The interest shall be paid from the fund or funds to which the overpayment was credited.
When the county treasurer makes the treasurer's annual settlement with the county auditor under division (D) of section 321.24 of the Revised Code, the treasurer shall certify to the auditor a list of all entries on the cumulative delinquent tax duplicate that are at that time in the process of being paid in installments under a valid delinquent tax contract. For each entry that appears on the duplicate that is not on the certified list, the auditor shall compute the full amount of interest charges which have accrued against such entry since the preceding such settlement was made and shall include such charges through the last day of the month preceding the current settlement. The auditor shall include such amounts on the tax list and duplicates prepared by the auditor as prescribed in section 5719.04 of the Revised Code unless the interest is less than one dollar, in which case it shall not be added to such tax lists and duplicates.
Before the county treasurer accepts any payment of taxes against which there are accrued interest charges that do not appear on the delinquent tax duplicate, the treasurer shall notify the auditor who shall issue a certificate to the treasurer showing the amount of such interest charges, and the treasurer shall collect the amount shown on such certificate at the time of accepting payment of such taxes. If the amount of such interest charges is less than one dollar, no such certificate shall be issued. In the case of delinquent personal property taxes, the interest shown on such certificate shall be credited to the undivided general tax fund, and distributed in the same manner as the delinquent taxes upon which the interest charges accrued. In the case of delinquent classified property taxes, the interest shown on such certificate shall be credited to the county public library fund and distributed in accordance with section 5747.48 of the Revised Code. When the payment of delinquent taxes is credited on the tax duplicate the treasurer shall make a separate notation thereon indicating the amount collected and the index number of the auditor's certificate herein prescribed.
R.C. §5719.041