Who is responsible for removing an old underground oil tank discovered after closing?

As a general starting point, an owner in possession of the land is the one who has to deal with an underground oil tank once it's discovered, regardless of when it was installed or by whom. Ontario's environmental protection framework can hold a current owner responsible for addressing contamination or hazards found on their own property, separate from any claim they might have against a previous owner.

Whether the new owner can recover the removal and any cleanup cost from the seller depends on what the seller knew and said. If the seller was aware of the tank and it created a hazardous or uninhabitable condition, failing to disclose it can support a claim for damages, particularly where the seller made a specific false statement about the property's condition or systems. If the seller genuinely didn't know, recovery becomes much harder. Buyers in older homes, especially where oil heat was once common, should ask directly whether the property was ever oil-heated and request any decommissioning records, since the physical tank is often the easier problem compared to any soil contamination underneath it, which may need separate testing and remediation.