Ohio Rev. Code § 3123.171
When a court renders a money judgment for child support, pursuant to a motion for a lump sum judgment filed by an obligee, interest shall accrue on that arrearage unless the court finds that it would be inequitable to assess interest. The interest shall accrue from the date the judgment is rendered to a date certain set for payment of the judgment at a rate specified in section 1343.03 of the Revised Code at the time the judgment is rendered. A court may assess interest on a child support arrearage prior to judgment pursuant to section 3123.17 of the Revised Code. The court shall enter the amount due, including interest, in the journal. If interest is not assessed, the court shall enter the reasons for not assessing interest in the journal.
R.C. § 3123.171