What You Must Disclose When Selling a Duplex in Ontario — And What You Don't

The Duty to Disclose in Ontario Real Estate

Ontario law requires sellers to disclose known material latent defects — defects that are not visible on inspection and that affect the property's habitability or value. This is distinct from patent defects (visible problems that a buyer should discover through inspection). The principle: you must disclose what you know and what you're aware could affect the buyer's decision, if it's not something they could discover themselves.

What You Must Always Disclose

Known water infiltration or flooding history (even if repaired), known mould presence or remediation history, known structural defects, any outstanding work orders or municipal violations, any legal disputes involving the property, and any zoning non-compliance you're aware of — including knowledge that the second unit is unpermitted. Failure to disclose known material latent defects can result in post-closing litigation for the full cost of remediation.

The Illegal Suite Question

This is the most contentious disclosure issue in Ontario duplex sales. If you know your second unit was never properly permitted, you are obligated to disclose this as it affects the property's legal status, financibility, and use. Many sellers try to avoid this by listing properties as 'in-law suite' or 'potential duplex' — but if you know the suite is unpermitted and fail to disclose, you're exposed to post-closing liability. Disclose and price accordingly.

What You Don't Have to Disclose

Patent defects (visible issues a buyer should find in inspection), facts that the buyer is obligated to investigate through their own due diligence (zoning, permit history), stigmatized property rules in Ontario (you do not have to disclose that a property was the site of a death or crime unless asked directly and specifically), and personal reasons for selling.

The Seller Property Information Statement (SPIS)

The SPIS is a voluntary form that sellers can complete disclosing known information about the property. It is NOT mandatory in Ontario. Completing a SPIS can be protective if you complete it accurately and fully, but it can create liability if you answer questions you don't have certain knowledge about. Many Ontario real estate lawyers advise against completing the SPIS unless you're very confident in all your answers. Discuss with your listing agent and lawyer before completing one.