What is Unjust Enrichment?

In Ontario family law, unjust enrichment is essentially the court’s way of saying: “You can't build a financial empire on someone else’s unpaid labour and then pretend they were just vibing nearby.” This equitable doctrine is designed to prevent one person from unfairly benefiting at another person’s expense — particularly after a relationship breaks down and one party minimizes or overlooks the other’s contributions.

What is unjust enrichment in Ontario family law? If you helped build the life, business, or home during a relationship, you may still have legal rights — even if assets are not in your name. Learn how unjust enrichment claims work after separation in Ontario. #OntarioFamilyLaw #UnjustEnrichment #PropertyDivision

For unmarried spouses, unjust enrichment claims are extremely important because common-law couples in Ontario do not automatically divide property the way married spouses do. Contrary to popular belief, there is no magical “three years together means I get half” rule. In most cases, each person leaves the relationship with whatever is in their own name unless the other spouse can prove an equitable claim like unjust enrichment. In other words, if your name is not on title, the court is not automatically handing you half the cottage simply because you assembled IKEA furniture there under emotional duress for six years.

To prove unjust enrichment, the claimant generally has to establish three things: first, that the other party received a benefit; second, that the claimant suffered a corresponding deprivation; and third, that there is no legal reason the other person should get to keep that benefit for free. Courts have found unjust enrichment in situations involving mortgage payments, renovations, unpaid labour, childcare, domestic responsibilities, and the deeply underappreciated contribution of essentially becoming the household operations manager while the other spouse accumulates wealth.

For married spouses, however, the law usually takes a different route. Ontario’s Family Law Act already contains a detailed equalization scheme intended to divide the financial gains of the marriage. Because of that, the Court of Appeal for Ontario held in Martin v. Sansome (2014) that unjust enrichment claims between married spouses will be fully addressed by equalization in the “vast majority” of cases. Translation: courts generally do not want spouses trying to order a second entrée of equitable relief after already being served the statutory property division meal. But family law has a remarkable talent for producing situations so chaotic that judges are forced to dust off legal principles nobody expected to use. Enter Mullin v. Sherlock (2023), a case that reads less like a routine property dispute and more like a judicial warning label about the dangers of refusing financial disclosure.

In Mullin, the wife gave up her architecture career to work for the husband’s company, contributed to growing the business, maintained the parties’ properties, and handled significant domestic responsibilities. According to the wife, she accepted lower compensation because the husband repeatedly assured her they were building a shared future together. The husband, meanwhile, argued that she was simply a salaried employee and that claims involving “joint family ventures” between married spouses were exceedingly rare — which is lawyer language for: “Please do not invent new ways for me to lose this case.”

The problem for the husband was that his financial disclosure failures were so severe that his Answer had already been struck by the court. In practical terms, he spent years refusing to provide the financial information necessary for the wife to properly pursue equalization, then attempted to argue that equalization was the proper remedy. This is roughly equivalent to hiding the ladder and then criticizing someone for not climbing onto the roof.

Justice Bloom ultimately concluded that this was one of those rare cases the Court of Appeal hinted might exist back in Martin v. Sansome. Because the wife was effectively prevented from advancing a proper equalization claim through no fault of her own, the court permitted her unjust enrichment claim to proceed. The result was extraordinary: the wife was awarded $3,000,000 in damages, representing 50% of the value of the husband’s company. The court found that her domestic and professional contributions were equal to the husband’s in creating the company’s success.

Cases like Mullin v. Sherlock will likely remain rare, but they are an important reminder that Ontario courts are deeply concerned with fairness — particularly where one party attempts to manipulate the litigation process through non-disclosure. Family law judges may be patient, but there are few things they dislike more than someone trying to weaponize secrecy while simultaneously asking the court for equitable treatment.

The broader lesson is simple: unjust enrichment exists to recognize contributions that mattered, even if they were not reflected on paper. Whether that contribution came through unpaid labour, sacrificing a career, maintaining a home, raising children, or helping build a business, courts are increasingly willing to look beyond formal ownership and ask the real question: who actually helped create the wealth?

If you are separating from a spouse or common-law partner and believe your contributions are being overlooked, strategic legal advice matters early. Unjust enrichment and property claims can become exceptionally complex where businesses, real estate holdings, non-disclosure, or unequal financial control are involved.

At Julia Fogarty, Estate & Family Litigation, we assist clients across Ontario with complex family law disputes requiring careful strategy, discretion, and sophisticated litigation counsel. We understand that these cases are rarely just about money — they are often about leverage, security, and protecting the future you helped build. To discuss your matter confidentially, contact our office to schedule a legal strategy session.