Negotiable but typically the seller. A failed drain field at inspection ($8K-$15K) usually pauses the deal until resolved. Some buyers will accept a price credit; others walk. Pre-listing inspections prevent surprises.
More detail
Greater Cincinnati real-estate practice: when a buyer's septic inspection reveals problems, the buyer's agent typically issues a request-for-repair notice. Three common outcomes follow. (1) Seller pays for the repair before closing, with proof of completion and a current-passing inspection. Most common outcome for moderate findings ($1,000-$5,000 scope). (2) Seller credits buyer at closing, with the buyer scheduling and managing the repair post-close. Common for findings that the buyer wants to combine with other planned work. (3) Buyer walks if the finding is severe (over $10,000) and the seller refuses to address it. Rare but does happen, particularly with FHA-financed buyers. Pre-listing inspection ($350-$550) eliminates surprises and lets the seller address findings on their own timeline rather than under the deal-pressure of an active escrow. Cincinnati sellers' negotiation reality: when a buyer's septic inspection finds problems, the most common outcome (60-70% of the time) is seller pays for the repair before closing. Less common (20-30%): seller credits buyer at closing for the buyer to manage the repair post-close. Rare (under 10%): buyer walks. Pre-listing inspection eliminates the surprise and lets the seller price-in any required repairs from the start. Sellers in Greater Cincinnati and Northern Kentucky should also order a pre-listing radon test in the same window because Zone 1 radon findings produce the second-most-common buyer credit request after septic issues, and bundling both inspections keeps the listing-prep cost predictable.