- A marriage contract (prenup) can be set aside under Family Law Act section 56(4) on specific grounds — it isn't automatically binding no matter what.
- The three grounds are: failure to disclose significant assets or debts, a party not understanding the nature or consequences of the contract, or general contract law grounds like unconscionability, duress, or undue influence.
- Ontario law requires a marriage contract to be in writing, signed, and witnessed — but independent legal advice is not a strict statutory requirement for validity.
- In practice, independent legal advice is the single biggest factor in whether a contract survives a challenge — its absence, or a defective version of it, is central to most successful challenges.
- The leading Ontario case, LeVan v. LeVan, 2008 ONCA 388, set aside a marriage contract due to significant non-disclosure and ineffective independent legal advice.
- Even where a s.56(4) ground is met, the court retains discretion to decide whether setting the contract aside is actually the right outcome.
The Short Answer
Yes, a prenuptial agreement can be set aside in Ontario — but only on specific, limited grounds under the Family Law Act, not simply because one party later thinks it's unfair. The single biggest factor in whether a marriage contract survives a challenge is whether both parties genuinely had independent legal advice when they signed it.
The Three Grounds Under Section 56(4)
Under section 56(4) of the Family Law Act, a court may set aside a domestic contract (including a marriage contract) on one of three grounds:
- Failure to disclose significant assets or significant debts or liabilities existing when the contract was made
- A party did not understand the nature or consequences of the contract
- Otherwise in accordance with the law of contract — general contract doctrines like unconscionability, undue influence, duress, or misrepresentation
Courts apply this as a two-stage test: first, whether one of these circumstances is established, and second, whether the court should actually exercise its discretion to set the contract aside, weighing the overall fairness of the agreement. The burden is on the party seeking to set the contract aside.
Failure to Disclose
Full and honest financial disclosure is central to a marriage contract's validity. If one party fails to disclose significant assets or debts that existed at the time the contract was made, this can be grounds for setting it aside — the theory being that the other party couldn't make an informed decision about what they were agreeing to without knowing the true financial picture.
Not Understanding the Contract
A party who genuinely did not understand the nature or consequences of what they were signing may have grounds to challenge it. This is closely tied to whether independent legal advice was provided — a party who received clear, independent legal advice explaining the contract\'s effect has a much harder time later arguing they didn\'t understand it.
General Contract Law Grounds
Beyond the two specific family-law grounds, a marriage contract can also be challenged using general contract law principles — unconscionability (a grossly unfair bargain combined with an inequality of bargaining power), undue influence, duress, or misrepresentation. These are the same doctrines that could unwind any contract, not something specific to marriage agreements.
Why Independent Legal Advice Matters So Much
The Family Law Act requires only that a domestic contract be in writing, signed by both parties, and witnessed — there is no strict statutory requirement for independent legal advice (ILA). In practice, though, ILA is described consistently as the single biggest factor in whether a contract survives a challenge. Courts look at whether each party had genuinely independent advice — from separate lawyers, without time pressure, with a real opportunity to understand and negotiate the terms — when assessing whether the “understanding” ground under s.56(4) is met.
LeVan v. LeVan: The Leading Case
In LeVan v. LeVan, 2008 ONCA 388, the Ontario Court of Appeal upheld a decision setting aside a marriage contract where the husband failed to disclose significant business and trust interests, and the wife's independent legal advice was found to be ineffective. The case established that once a s.56(4) ground is met, the court can weigh the overall fairness of the contract in deciding whether to exercise its discretion to set it aside — it remains the key Ontario authority on marriage contract disclosure obligations.
Common Mistakes
Marriage contracts can be challenged on specific grounds — signing one doesn't guarantee it will hold up unchanged.
This is the single biggest factor in whether a contract survives a later challenge — skipping it is a false economy.
Failing to disclose significant assets or debts can unravel the entire agreement later, regardless of intent.
A marriage contract signed days before the wedding, without time to properly review and get advice, is more vulnerable to a later challenge.
Considering or challenging a marriage contract? Call our Toronto family lawyers at 416-274-2222 for a free consultation.
Frequently Asked Questions
Yes, but only on specific grounds under section 56(4) of the Family Law Act — it isn't enough to simply argue the agreement feels unfair. A party seeking to set aside a marriage contract must establish one of the recognized grounds and then persuade the court that setting it aside is the appropriate outcome.
Three grounds: (1) failure to disclose significant assets or debts that existed when the contract was made, (2) a party not understanding the nature or consequences of the contract, or (3) general contract law grounds — such as unconscionability, undue influence, duress, or misrepresentation.
Not as a strict legal requirement — the Family Law Act requires only that the contract be in writing, signed by both parties, and witnessed. However, independent legal advice is, in practice, the single most important factor in whether a contract survives a later challenge.
Courts frequently look at whether each party had genuinely independent legal advice when assessing whether they truly understood the contract's nature and consequences — one of the s.56(4) grounds. A missing or defective independent legal advice process is a common thread in cases where marriage contracts have been set aside.
The Ontario Court of Appeal upheld a decision setting aside a marriage contract due to the husband's failure to disclose significant business and trust interests, combined with ineffective independent legal advice for the wife. It remains the leading Ontario case on marriage contract disclosure obligations.
This is assessed based on the specific facts — generally, the failure to disclose assets or debts substantial enough that, had they been known, they could reasonably have affected the other party's decision to sign the agreement or its terms.
Not automatically. Courts apply a two-stage approach: first, whether one of the grounds is established, and second, whether the court should actually exercise its discretion to set the contract aside, considering the overall fairness of the agreement and the circumstances.
Full and honest financial disclosure from both parties, genuinely independent legal advice for each person (not the same lawyer, and not advice given under time pressure), and a contract that isn't so one-sided that it invites a fairness challenge, are the most important practical steps.