Can Prenuptial Agreements Be Overturned? What Makes It Invalid?
Interest in prenuptial agreements remains high among younger Canadians. A 2026 TD survey found that 51% of Gen Z respondents would want their partner to sign one.
With people marrying later in life, many enter relationships with established careers, properties, and savings they want to protect. But while prenups are designed to offer clarity, they aren’t always ironclad.
In Ontario, a prenup is legally known as a marriage contract. Courts generally respect these agreements, but the Family Law Act allows all or part of one to be set aside in specific circumstances.
When Can a Prenup Be Overturned in Ontario?
Prenuptial agreements in Ontario fall under the Family Law Act. Section 56(4) identifies three main grounds for setting aside a marriage contract or one of its provisions. These involve financial disclosure, understanding the agreement, and other grounds available under contract law.
Lack of Full Financial Disclosure
If one spouse hides assets, debts, or income, the other spouse may argue that they agreed to the contract under false pretenses. Ontario courts take financial dishonesty seriously and invalidate the whole prenup. You must disclose all your assets, properties, and salary before signing the agreement.
Not Understanding the Agreement
A court may intervene if one spouse did not understand the nature or consequences of the agreement. This can become relevant when the terms are complex or one spouse had little opportunity to review them.
Duress, Pressure, or Other Contract Law Issues
Section 56 also allows a court to apply general contract law. Claims involving duress, undue influence, fraud, or misrepresentation may therefore affect whether the agreement remains enforceable.
Signing shortly before the wedding does not automatically invalidate a prenup. The surrounding circumstances and the pressure placed on the person will matter.
Can a Prenup Be Set Aside Because It Seems Unfair?
An unequal result does not automatically make a marriage contract invalid. Fairness alone is not one of the grounds listed in section 56(4).
However, the terms may become relevant once a legal ground for setting aside the agreement has been established. Separate rules can also apply to spousal support provisions.
Lack of Independent Legal Advice
Ontario law does not make independent legal advice a formal requirement for every marriage contract. However, each spouse should obtain advice from their own family lawyer before signing.
A lack of independent advice may become important if someone later claims they misunderstood the agreement or signed under improper pressure.
The Agreement Does Not Meet Ontario’s Formal Requirements
Under section 55 of the Family Law Act, a marriage contract must be in writing, signed by both parties, and witnessed. An agreement that does not meet these requirements is unenforceable.
Vague or contradictory wording can also lead to disputes about how a particular provision should be interpreted.
What a Prenup Cannot Override in Ontario
A marriage contract cannot determine decision making responsibility or parenting time. Those decisions remain subject to the child’s best interests.
Courts may also disregard a child support provision if it is unreasonable under the applicable Child Support Guidelines.
Ontario law also limits what a marriage contract can say about the matrimonial home. A provision that attempts to restrict a spouse’s rights under Part II of the Family Law Act is unenforceable.
If you have concerns about your prenup, a family lawyer can review how the agreement was prepared, the disclosure exchanged, and the terms being challenged.
Book a consultation with Noori Law today.
