Prenuptial Agreement in
Ontario
In Ontario, prenuptial agreements are legally called "marriage contracts" — a type of domestic contract governed by the Family Law Act. Rather than a straightforward division of assets, Ontario uses an equalization of net family property system: at the end of the marriage, each spouse calculates the growth in their net worth during the marriage, and the spouse whose net worth grew more pays half the difference to the other. A marriage contract allows couples to modify these default rules, but Ontario law contains one firm restriction that cannot be contracted around: a marriage contract cannot limit a spouse's right to possession of the matrimonial home.
Property division
How Ontario handles marital property
Ontario divides property through "equalization of net family property" under the Family Law Act. Each spouse calculates the growth in their net worth during the marriage, and the spouse with the higher growth pays half the difference to the other.
Legal framework
Provincial family law in Ontario
Prenuptial agreements in Ontario (called "marriage contracts") are governed by the Family Law Act. The agreement must be in writing, signed by both parties, and witnessed. Marriage contracts cannot limit a spouse's right to possession of the matrimonial home.
Ontario has important special rules: (1) A marriage contract cannot limit a spouse's right to possession of the matrimonial home. (2) The equalization system means you cannot simply agree to keep your own property; instead, you address how net family property will be calculated. (3) Independent legal advice is strongly recommended and significantly strengthens enforceability.
Requirements
What makes a prenup valid in Ontario
Understanding these requirements helps ensure your agreement will hold up when it matters most.
Notarization
Notarization is not required but is recommended. The key requirement is that the agreement must be witnessed.
Witnesses
Each party's signature must be witnessed. This is a mandatory requirement under the Family Law Act.
Timing
No specific statutory timing requirement. The agreement should be signed well before the wedding to demonstrate voluntariness.
Spousal Support
Spousal support waivers are difficult to enforce in Ontario. Courts retain broad discretion under both the Family Law Act and the federal Divorce Act to award spousal support.
Coverage
What your Ontario prenup can address
A prenuptial agreement in Ontario can cover a wide range of financial and property matters.
Best practices
Tips for a strong prenup in Ontario
Following these best practices helps ensure your agreement is clear, fair, and enforceable.
Both parties must each have their own Ontario family law lawyer — independent legal advice is particularly critical in Ontario because the equalization system is complex and a lawyer can ensure your agreement works correctly within the statutory framework.
Understand that your Ontario marriage contract cannot limit either spouse's right to possession of the matrimonial home during the marriage; structure any provisions about the family home with this limitation in mind.
Disclose all assets and debts fully in writing before signing — Ontario courts treat inadequate financial disclosure as one of the primary grounds for setting aside a marriage contract.
Sign the contract well in advance of the wedding; courts in Ontario examine whether any time pressure surrounded the signing and whether both parties had genuine opportunity to review and negotiate.
Work with your lawyer to ensure the agreement addresses the equalization calculation specifically, not just property ownership, because Ontario's net family property system means who "owns" an asset is only part of the picture.
FAQ
Common questions about prenups in Ontario
What is a prenuptial agreement called in Ontario?
In Ontario, the agreement is formally called a "marriage contract" and is classified as a type of domestic contract under the Family Law Act. The terms "prenuptial agreement" and "prenup" are widely understood but are not the legislative terminology. An Ontario marriage contract must be in writing, signed by both parties, and witnessed — witnessing is a mandatory statutory requirement, not merely a recommendation.
What cannot be included in an Ontario marriage contract?
An Ontario marriage contract cannot limit or override a spouse's right to possession of the matrimonial home. This is a statutory protection set out in the Family Law Act that parties cannot contract out of. Additionally, marriage contracts cannot contain provisions that purport to direct the custody or access arrangements for children born of the marriage, as those matters are always decided based on the best interests of the child.
How does Ontario's net family property equalization work with a prenup?
Under the Ontario Family Law Act, the default rule is that each spouse calculates their net family property — the growth in their net worth during the marriage — and the higher-value spouse pays half the difference to the other. A marriage contract can modify this by specifying which assets are excluded from each spouse's net family property calculation, allowing assets brought into the marriage or received as gifts to remain separate from equalization.
Does an Ontario marriage contract need to be witnessed?
Yes — witnessing is a mandatory requirement under the Ontario Family Law Act, not merely a best practice. Each party's signature must be witnessed by at least one person. Unlike some other provinces, this is a statutory condition of validity. Notarization is not required by statute but is commonly done as an additional protective measure.
Can an Ontario marriage contract waive spousal support?
An Ontario marriage contract can include spousal support provisions, but courts in Ontario retain broad discretion under both the Family Law Act and the federal Divorce Act to award support regardless of what the contract states. Ontario courts are particularly willing to override spousal support waivers when a significant amount of time has passed and circumstances have changed considerably since the contract was signed.