It depends on the county rather than the state. Several county health districts in this market require a point-of-sale evaluation before transfer, and lenders often require one regardless. Confirm with the district before listing.
More detail
Ohio does not impose a single statewide point-of-sale septic inspection requirement, so the answer comes from the county health district that holds the permit for the property. Requirements across Hamilton, Butler, Warren, and Clermont counties are not uniform, and they have tightened in several districts over the past decade. On the Kentucky side of this market, covering Boone, Kenton, and Campbell counties, the requirement is likewise administered locally rather than at the state level, so a seller crossing the river is asking a different office the same question. Three things drive an inspection even where the county does not mandate one. The lender may require it, particularly on FHA and VA loans, which routinely call for a septic evaluation and sometimes a well test alongside it. The buyer's agent will normally ask for one as a contingency. And the seller disclosure form asks about known conditions of the system, which is easier to complete honestly with a recent evaluation than without. Practically, listing without an evaluation moves the inspection to the buyer's timeline. That means it happens during the response window, with the buyer choosing the inspector, and any finding becomes a negotiation from the weaker side. Sellers who evaluate before listing have time to pump, replace a baffle, or fit an effluent filter, and can put a clean report in the listing file. Septic permits, as-built drawings, and any point-of-sale requirement are held by the county health district covering the property, and they differ between districts across Hamilton, Butler, Warren, and Clermont counties. One timing note: evaluations are best done when the system has been in normal use. An evaluation on a vacant house tests very little.