If you’re selling a home in one of the roughly 37 states with radon disclosure requirements for sellers, you must give the buyer, in writing and before or at contract signing, any radon test results you have, the dates and locations of those tests, and documentation of any mitigation system installed in the home. You generally don’t have to order a new test just because you’re selling, but you cannot withhold what you already know. Radon is a colorless, odorless radioactive gas that the EPA estimates causes about 21,000 lung cancer deaths in the United States each year, which is why these laws exist in the first place.1U.S. Environmental Protection Agency. Radon Is the Second Leading Cause of Lung Cancer
What the Disclosure Form Actually Asks
State disclosure forms vary, but the core questions are consistent. Has radon testing ever been performed on the property? What were the results, reported in picocuries per liter? Was a mitigation system installed, and is it still operating? If the answer to the testing question is no, most forms include a “no knowledge” checkbox so the topic still appears on the record.
Results at or above 4.0 pCi/L deserve particular care. That number is the EPA’s action level, the point at which the agency recommends fixing the home, and it is the figure that shows up on disclosure forms and in state statutes.2U.S. Environmental Protection Agency. What Is EPAs Action Level for Radon and What Does It Mean A result at or above 4.0 pCi/L must be clearly indicated on the form; a result between 2.0 and 4.0 pCi/L should still be disclosed, because the EPA recommends homeowners consider mitigation in that range as well.
For each test, report the date, the location in the home where the device was placed, and whether the test was conducted by a certified professional or with a DIY kit. If a mitigation system has been installed, disclose who installed it, when, and whether any post-mitigation testing confirmed the system brought levels below 4.0 pCi/L.
Age of the data doesn’t excuse omission. If your most recent test is several years old, include it. The buyer and their agent can then decide whether to request a fresh test during the inspection period.
When the Disclosure Must Reach the Buyer
In most states the rule is the same: the radon disclosure has to be in the buyer’s hands before or at the time the purchase contract is signed. Delivering it early lets the buyer price radon into their offer or negotiate a testing contingency. Dropping it on them at closing, after they’ve already committed, is the pattern that leads to lawsuits.
Most sales handle delivery through real estate portals or secure email that generate timestamps for when the documents were sent and opened. The buyer signs an acknowledgment confirming receipt, which creates the formal record that the seller met the duty. Agents on both sides usually manage this exchange, but the legal obligation sits with the seller. If an agent drops the ball and the form never reaches the buyer, the seller is the one holding the liability.
Some states also require the seller to hand over a state-published radon information pamphlet along with the disclosure form. Check your state real estate commission’s website for the current form, any required attachments, and the specific delivery deadline.
No Federal Mandate, State-by-State Rules
There is no federal law requiring a seller to test for radon or disclose results in a standard single-family home sale. The EPA publishes a Home Buyer’s and Seller’s Guide to Radon that recommends sellers share any existing results and buyers test before purchasing, but that is guidance, not a mandate.3U.S. Environmental Protection Agency. Home Buyers and Sellers Guide to Radon For FHA-insured mortgages, HUD requires lenders to give prospective buyers a home inspection form that mentions radon at first contact.4U.S. Environmental Protection Agency. Radon and Real Estate Resources
State legislatures carry the actual disclosure duty. Approximately 37 states and the District of Columbia have enacted some form of radon disclosure requirement for residential real estate transactions. Specifics differ, but the common pattern is that any seller knowledge of testing, results, or mitigation systems must be shared with the buyer in writing before or at contract signing. A home on one side of a state line can carry a detailed signed-disclosure requirement while a home across the border has none, though general property condition disclosure statutes may still apply even where radon isn’t named specifically.
Documents That Back Up the Disclosure
A checked box on a form is the minimum. What protects a seller from later claims is the paper underneath it. Attach the original lab report for each test, including the chain of custody if a professional conducted it. If a mitigation system is installed, attach the installation invoice, the contractor’s information, the system warranty, and any post-mitigation test results.
The strength of the underlying test matters, too. A professionally conducted short-term test with a documented chain of custody is far more defensible than a homeowner-placed charcoal kit with no lab report. Professional short-term testing typically runs $300 to $600; DIY kits are cheaper but carry less weight in a negotiation or a courtroom. If the only test you can point to is a years-old DIY kit, assume the buyer will want a fresh professional test regardless of what you disclose, and plan accordingly.
Keep signed copies of the disclosure form and the buyer’s acknowledgment in your closing file. Statutes of limitations for failure-to-disclose claims generally fall between two and ten years, so holding onto those records for at least a decade is reasonable insurance.
What Happens If You Don’t Disclose
A seller who hides known test results or lies on the disclosure form faces civil liability that can far exceed the cost of the mitigation system they were trying to avoid. The baseline claim is failure to disclose a known defect, which in most states lets the buyer recover remediation costs. A basic active soil depressurization system runs roughly $800 to $2,500 for most single-family homes, and the fan adds $150 to $500 a year in electricity.5U.S. Environmental Protection Agency. How Much Can a Radon Mitigation System Cost Add attorney fees, expert witnesses, and the buyer’s own testing bills, and the total climbs fast.
If the seller actively concealed results or falsified the form, the claim escalates to fraud or fraudulent misrepresentation. Courts treat deliberate concealment more harshly than simple omission. In extreme cases, with very high radon levels and clear evidence of intentional deception, a court may rescind the entire purchase contract, unwinding the sale and returning both parties to where they started. That outcome is relatively rare but it is on the table when the facts are bad enough.
Property value diminution is a separate category of damages. A home with a documented history of elevated radon and no mitigation may appraise below the sale price, and the difference becomes a recoverable loss. The seller’s real estate agent can face liability too if they knew about the problem and failed to make sure the disclosure form reached the buyer. Agents carry an independent duty to facilitate disclosures, and “the seller never told me” only works as a defense when it’s actually true.
How Buyers Typically Respond
Even a clean seller disclosure rarely ends the radon question. Buyers routinely order their own short-term radon test as part of the home inspection contingency, and the test fits comfortably inside a standard inspection window because results come back in 2 to 5 days.
If the buyer’s test comes in at or above 4.0 pCi/L, the common outcomes are a seller-funded mitigation system installed before closing, a closing credit so the buyer can hire their own contractor after closing, or a price reduction reflecting remediation cost. If the seller refuses to address an elevated result, a buyer with an active inspection contingency can walk and recover their earnest money. For most sellers, paying for the system is cheaper than losing the deal and relisting with a known radon issue that now has to be disclosed to every future prospect.
A Note on Rental Properties
Radon disclosure obligations in rentals are a separate track from home sales, but worth knowing if you own both. A handful of states have extended written-disclosure duties to landlords before lease signing, ranging from handing over a state radon pamphlet to disclosing all known results and allowing tenants to test. In at least one state, tenants who discover elevated levels can terminate the lease with 30 days’ notice. Even in states without a radon-specific rental law, a landlord who knows about high levels and stays silent risks claims under the implied warranty of habitability or premises liability.
Federally assisted housing operates under different rules. Under a HUD policy effective for non-tribal recipients since April 2024 and tribal recipients since January 2026, programs following the Multifamily Accelerated Processing Guide and certain other handbooks must test for radon and mitigate any unit testing at or above 4.0 pCi/L, on a per-unit basis.6HUD Exchange. FAQ – HUD Policy for Addressing Radon in the Environmental Review Process A building cannot average its units’ results to avoid mitigating the ones that tested high.
For a standard single-family sale, the controlling question is still your state’s disclosure statute and whatever information you already have in a drawer about this specific house. Put all of it on the form, attach the paperwork, and get the buyer’s signed acknowledgment before the contract is signed.