Ohio Rev. Code § 3937.33
An insurer may cancel an automobile insurance policy at such time prior to its expiration for such reasons as may be permitted by section 3937.31 of the Revised Code, by mailing to the insured, at the insured's last known address appearing on the insurer's records, a notice of cancellation pursuant to section 3937.32 of the Revised Code. If such notice of cancellation, for a reason other than nonpayment of premium, does not contain an explanation of the reason for cancellation and the information upon which it is based, the insurer shall, within five days after receipt of the written request therefor by the insured, furnish explanation to the insured in writing. Prior to the effective date of cancellation, the insurer shall refund to the insured any premium and other sums which may be due the insured.
Upon compliance by the insurer with all requirements of this section, such automobile insurance policy is cancelled on the effective date stated in the notice of cancellation, except as otherwise provided in section 3937.35 of the Revised Code. In the event of the insurer's failure to comply with any requirement of this section, such cancellation shall be ineffective and the policy shall continue in force until such time as it is cancelled or otherwise terminated pursuant to law and the terms of the policy.
R.C. § 3937.33