When couples in Ontario sign what is commonly known as a pre-nuptial agreement (prenup), but in Ontario are officially referred to as marriage contracts and cohabitation agreements, they often do it to avoid future conflict. But what if you signed one and later feel it wasn’t fair—or even valid? The law does give people a chance to challenge these agreements, but only in specific situations.
Let’s break it down in simple terms.
The following should not be taken as legal advice. For legal advice on marriage contracts, please contact HCLS today.
When Can a Marriage Contract Be Set Aside?
In Ontario, the court can set aside (annul) a marriage contract or cohabitation agreement if one or more of these things happened when it was made:
- Important financial information was hidden – If your partner didn’t tell you about major assets, debts, or income, that’s a problem—especially if it influenced your decision to sign the agreement.
- You didn’t understand what you were signing – This includes not understanding how the agreement would affect your rights and future. For example, did you know what “equity” meant? Did you even read the agreement carefully? Did you get legal advice?
- There was pressure, trickery, or other unfair behaviour – If you were pressured into signing (also called duress) or misled about something important, a judge might decide the agreement isn’t valid.
Proving It’s Unfair Is Not Easy
You’ll need evidence to back up your claim. For example, saying “I didn’t understand it” won’t be enough if you had your own lawyer and time to review it. If the contract wasn’t witnessed or signed properly, that might help—but it’s not an automatic win.
Courts also look at the big picture: Did both people benefit from the agreement? Was anything hidden? Did you raise concerns right away or wait years before complaining?
After a Death, It Gets More Complicated
If the person you signed the agreement with has passed away, it’s even harder to challenge the contract. You’ll need extra proof, since the other person isn’t around to confirm what happened.
What Should You Do Now?
If you’re thinking about challenging a marriage contract or cohabitation agreement, the Home Counsel Legal Services (HCLS) team is ready to help. HCLS’s team understands how to navigate the complex issues surrounding evidence related to marriage contracts and cohabitation agreements. Our team takes the time to explain your rights in plain language and guide you through each step of the process. Whether you’re questioning the fairness of an existing agreement or responding to a challenge against one, HCLS is here to provide trusted, accessible legal support that helps you make informed decisions and protect your future.
This blog post was authored by Matthew Patten, Student-at-law with HCLS.
