Unjust Enrichment Claims in Ontario

Not every unfair outcome comes from a broken contract. Sometimes one person ends up benefiting from another’s money, work, or property without any valid agreement covering the situation — or without a contract at all. Unjust enrichment is the legal doctrine Ontario courts use to address exactly this kind of situation, allowing a court to require the person who received the benefit to pay for it, even where no breach of contract can be proven.

The doctrine exists because contract law alone doesn’t cover every situation where fairness demands a remedy. Two people might work together on a venture without ever signing an agreement, a deal might fall apart before a formal contract is finalized, or a person might contribute significant money and labour toward a property that ends up being registered in someone else’s name alone. Unjust enrichment fills the gap contract law leaves open in these situations.

It’s important to understand that unjust enrichment is a distinct legal theory, not a backup version of breach of contract. It has its own test, and succeeding on it doesn’t require showing that anyone broke a promise — only that someone kept a benefit they shouldn’t fairly be allowed to keep.

The doctrine is sometimes described using the broader term restitution, which refers to the general area of law concerned with requiring a party to give back a benefit it received rather than keep it. Unjust enrichment is the main vehicle through which Ontario courts grant restitution outside of a valid contract, and the two terms are often used together in court decisions addressing these claims.

Ontario courts generally analyze unjust enrichment claims using a three-part test. First, there must be an enrichment of the defendant — they received something of value, whether money, property, services, or work. Second, there must be a corresponding deprivation suffered by the claimant — the benefit the defendant received came directly at the claimant’s expense, not from some unrelated source.

The third element is usually where disputes are actually won or lost: the absence of a juristic reason for the enrichment. A juristic reason is a valid legal basis justifying why the defendant is entitled to keep the benefit. A valid, applicable contract is the most common juristic reason — if a contract already explains and justifies why the defendant received what it did, there’s generally no room for an unjust enrichment claim covering the same benefit. A freely given gift, or an obligation imposed by another area of law, can also serve as a juristic reason.

All three elements generally need to be proven. A claimant who can show enrichment and deprivation but can’t overcome a valid juristic reason the defendant points to will generally not succeed, no matter how unfair the outcome might feel on its face.

A breach of contract claim starts from a valid agreement and asks whether one party failed to live up to a specific promise within it. Unjust enrichment starts from a different place entirely — it doesn’t require any contract, and it doesn’t ask whether a promise was broken. It asks only whether one party ended up holding a benefit, at another’s expense, without a fair legal basis for keeping it.

This difference matters practically. Where a valid contract clearly covers the situation, that contract is usually the juristic reason that defeats an unjust enrichment claim over the same benefit — the parties already agreed on the terms, so the law generally won’t layer an additional claim on top. Unjust enrichment becomes most useful where a contract is missing, invalid, incomplete, or disputed, or where the benefit in question falls outside anything the contract actually addressed.

Because of this overlap, many claimants plead breach of contract and unjust enrichment together as alternatives, letting a court decide which theory actually fits once the facts and any contract terms are sorted out. See our overview of breach of contract in Ontario for how that claim is generally structured.

Unjust enrichment claims tend to arise in a recurring set of situations. One of the most common is work performed without a signed contract — a contractor who starts work based on a verbal understanding that is never formalized, or a consultant who continues providing services after a written agreement expires, and the client then refuses to pay for the value received.

Failed deals are another frequent source. A buyer who pays a deposit or begins performing obligations before a transaction falls apart, where the underlying contract turns out to be invalid or unenforceable, may be left with no contract claim but a strong unjust enrichment argument if the other side keeps money or benefits without giving anything back.

Business relationships generate their own version of the problem — a party that contributes capital, inventory, or unpaid effort toward a joint venture that never formalizes a partnership agreement, only to see the other party keep the benefit of that contribution if the venture doesn’t work out as planned.

Family arrangements involving aging relatives raise a related pattern: an adult child who moves in with a parent and takes on caregiving duties, or contributes toward renovations or household expenses, based on an understanding — often unwritten — that they would eventually inherit or share in the property. Where that understanding later proves mistaken, or is disputed by other family members, unjust enrichment can provide a route to recognizing the value of what was actually contributed.

One of the most significant modern uses of unjust enrichment in Ontario involves contributions to property registered in someone else’s name. This commonly arises between unmarried partners, or within families, where one person puts significant money, labour, or both into a home or property that ends up registered solely in the other person’s name, often without either side thinking carefully about the legal consequences at the time.

If the relationship or arrangement later breaks down, the person who isn’t on title can be left with no direct ownership claim through property law alone. Unjust enrichment — often paired with a related equitable remedy called a constructive trust — gives courts a tool to recognize the contribution, either through monetary compensation or, in some cases, by recognizing an actual interest in the property itself.

These cases tend to be fact-heavy and turn significantly on the evidence available showing exactly what was contributed, when, and under what expectations. Clear records of payments, renovation costs, and the understanding between the parties at the time generally make these claims far more straightforward to assess.

The most common remedy is monetary compensation reflecting the value of the benefit the defendant retained — sometimes measured by what it would have cost the defendant to obtain that same benefit elsewhere, and sometimes by the value the claimant actually gave up providing it. The exact approach depends on the facts of the specific claim.

In some property-related cases, particularly where a claimant’s money or labour went directly into acquiring, maintaining, or improving a specific property, a court can go further and recognize an actual proportional interest in that property through a constructive trust, rather than limiting the claimant to a cash payment. This remedy is generally reserved for situations where a monetary award alone wouldn’t fairly reflect the claimant’s contribution.

As with other contract-adjacent disputes, the size and complexity of an unjust enrichment claim generally shapes the best venue for pursuing it — smaller, more straightforward claims are often suited to Small Claims Court, while property-related or complex business claims are typically better suited to the Superior Court of Justice. Our contract disputes hub and contact page can help point toward further resources.