Neither Ohio nor Kentucky requires a septic inspection to sell a house. Both states require you to disclose the system type and known problems on the seller's disclosure form, and buyers' lenders or contracts often require an inspection, which several local health departments perform on request.
More detail
Start with what is mandatory. Ohio's residential property disclosure form, required by Revised Code 5302.30, asks you to check the type of system (septic tank, leach field, aeration tank, filtration bed, or another), give the date of the last inspection and who performed it, and describe any known leaks, backups, or material problems. Kentucky's Seller's Disclosure of Property Condition (KREC Form 402) sorts systems into categories such as a single-home aerobic unit or a septic tank with a drain field, then asks for the servicer's name, the last septic inspection date, the date the tank was last cleaned, and any known problems, and it separately asks about old septic tanks or field lines on the property. No statewide point-of-sale inspection exists in either state: Ohio's rules refer only to locally established real estate transfer programs, and Kentucky's 902 KAR 10:085 has no sale provision. Locally, Hamilton County Public Health offers a voluntary real estate inspection at $225 a visit, and its online map shows every system's recent inspection history; Clermont County Public Health performs homeowner-requested inspections for $200 and notes that buyers request them most often and some lenders require them; the Northern Kentucky Health Department's existing-system inspection request form lists a $200 fee; and the Warren and Butler county fee schedules list no point-of-sale septic inspection. Keep in mind that a county compliance inspection is not the same as a full evaluation with the tank pumped. A practical order for sellers: pull your county record, pump and evaluate the system about two months before listing, fix small items with receipts, find and mark the lids, and fill in the disclosure form from those documents. Our septic inspection page covers a pre-listing evaluation, the seller repair FAQ covers what happens if a buyer finds a problem, and our county permit guide lists who to call in each county.