Marriage Contract Ontario: What It Covers, What It Can't Do, and How to Get One

A marriage contract in Ontario is a legal agreement signed under Part IV of the Family Law Act R.S.O. 1990, c. F.3 that sets the financial rules for a marriage. It defines what happens to property, how spousal support works, and what each person walks away with if you separate or one of you dies. In Ontario, "marriage contract" is the legally correct term for what most people call a prenup.

If you're new to the concept, start with what a prenup is and what it covers across Canada. This article covers what's specific to Ontario: the rules, the limits, the case law, and how to get one done correctly.

What can a marriage contract cover in Ontario?

Under section 52(1) of the Family Law Act, a marriage contract can address a wide range of financial matters. The most commonly used provisions fall into six categories.

Property division. Which assets each person keeps at separation, including property owned before the marriage. How property acquired during the marriage is divided. Custom treatment of the matrimonial home — defining how pre-marriage equity is handled and establishing valuation formulas for growth. Treatment of inheritances received during the marriage.

Spousal support. A marriage contract can waive spousal support entirely, cap its duration or amount, or set a formula tied to the Spousal Support Advisory Guidelines. It can also include career interruption compensation — agreeing in advance how a spouse who pauses their career for family will be compensated through enhanced support or a larger property share. This is one of the most practically important provisions for couples where one partner plans to reduce paid work for caregiving: the motherhood penalty costs roughly 4–7% in wages per child and up to 18–20% of career earnings for each year out of the workforce. Defining compensation in advance, when both parties are at the table equally, produces better outcomes than litigating it later.

Pensions and retirement accounts. Excluding pre-marriage pension accrual from equalization. Defining the valuation method for defined-benefit pensions — which can be worth $500,000 to $2 million or more for long-career public sector workers. RRSP and TFSA treatment at separation.

Business interests. Pre-agreed valuation methodology (multiple of EBITDA, book value, or certified business valuator appraisal). Caps on how much business equity is shared at separation. Protection against a forced sale if valuation is disputed — contested business valuations alone can cost $30,000–$100,000 in legal fees.

Death provisions. Under section 5(2) of the Family Law Act, a surviving spouse has the right to claim equalization of net family property on the death of their partner — the same calculation that applies at separation. A marriage contract can waive this claim, which matters significantly for blended families where children from prior relationships need the estate protected. These death provisions work alongside a will, not instead of one.

Debt responsibility. Confirming that pre-marital debt stays with the person who brought it in. Setting thresholds for incurring joint debt during the marriage.

What a marriage contract cannot cover in Ontario

Three things are either void or constrained by statute regardless of what the agreement says.

Child custody and child support. Any clause purporting to predetermine custody or child support is void under the Family Law Act. Courts determine both based on the best interests of the child at the time of separation. Including these clauses doesn't invalidate the rest of the contract — but they have no legal effect, and their presence can signal to a court that the agreement was drafted without care.

The right to live in the matrimonial home. Under section 26(1) of the Family Law Act, both spouses have equal rights of possession of the matrimonial home during the marriage — regardless of who holds title and regardless of what a marriage contract says. A marriage contract can define how the home's value is treated at separation. It cannot remove a spouse's right to live there while the marriage continues.

Absolute spousal support waivers in certain circumstances. Under section 33(4) of the Family Law Act, courts can override a spousal support waiver if enforcing it would leave one spouse in financial hardship serious enough to require social assistance. A blanket "no support, ever" waiver with no conditions is the most vulnerable type. A carefully structured, SSAG-anchored provision — reflecting the actual financial situation of both parties at signing, with full disclosure and ILA — is substantially harder to set aside.

CPP credit splitting. One frequently overlooked limitation: under section 55.1 of the Canada Pension Plan, CPP credit splitting on divorce is mandatory upon application by either spouse and cannot be prevented by a marriage contract. Ontario has not enacted the opt-out legislation available in BC, Alberta, and Saskatchewan. A marriage contract can address most pension assets — but not CPP credits accumulated during the marriage.

The matrimonial home rule — Ontario's most important and least understood provision

This is the single most consequential family law rule for anyone entering marriage with property in Ontario, and the one that surprises almost everyone who encounters it.

Under section 4(1) of the Family Law Act, the value of a spouse's ownership interest in the matrimonial home on the date of marriage cannot be deducted as an excluded asset when calculating net family property. In plain language: even if you bought your home entirely before you met your partner, your pre-marriage equity is not automatically protected at separation.

What this means in practice:

You buy a Toronto condo for $600,000 before the marriage. Your equity at the time is $200,000. During the marriage the condo appreciates to $900,000 and your equity grows to $500,000. At separation — without a marriage contract — your partner is entitled to share in the equalization of the entire $500,000, including the $200,000 you built before they were in the picture.

This is different from BC, where pre-relationship property is "excluded property" under the Family Law Act SBC 2011, and it contradicts most people's intuition about what "I owned it before we married" means.

A marriage contract can address this directly. Common approaches: defining the pre-marriage equity as excluded from equalization, setting a custom sharing formula for appreciation during the marriage, or offsetting the home's equity against other assets so the titled owner isn't forced to sell.

What a marriage contract cannot do: remove the non-owning spouse's possessory right under section 26(1). During the marriage, both spouses have equal rights to live in the home regardless of title or what the contract says. The contract governs the financial outcome at separation — not occupancy while the marriage continues.

For additional scenarios and a deeper explanation, see how the matrimonial home is treated at separation in Ontario.

What makes a marriage contract enforceable in Ontario?

Ontario courts routinely uphold properly executed marriage contracts. The agreements that get set aside almost always fail for procedural reasons, not because of what they say. In Dougherty v. Dougherty (2016 ONCA 781), the Ontario Court of Appeal confirmed this directly: mere inequality of outcome is not sufficient to set aside a contract — the court must find a procedural defect.

The three most common grounds for setting aside under section 56(4) of the Family Law Act:

1. Inadequate financial disclosure. Both parties must disclose all significant assets, debts, income, and liabilities before signing. This is the single most common and successful challenge ground in Ontario. In LeVan v. LeVan (2008 ONCA 388), the Ontario Court of Appeal set aside a marriage contract partly because of incomplete disclosure. Full, documented disclosure is not a formality — it's the foundation the entire agreement rests on, and any omitted asset is a potential attack vector years later.

2. No Independent Legal Advice. Each party needs their own independent Ontario lawyer to review the agreement before signing. ILA is not technically mandated by the Family Law Act the way it is in Alberta, but Ontario courts treat its absence as a serious problem. A 2003 Ontario Superior Court decision stated that upholding an agreement where one party had no ILA would be "the exception and not the rule." In Hartshorne v. Hartshorne (2004 SCC 22), the Supreme Court of Canada confirmed that the presence of ILA is the strongest indicator of voluntariness — and that courts should be reluctant to second-guess agreements made with it.

3. Duress or timing. An agreement signed in the days before a wedding — especially under pressure — is significantly more vulnerable than one negotiated months in advance. Courts look carefully at the full circumstances of how and when an agreement was signed.

One further point on clause survival: Ontario courts treat property and support provisions differently. Property clauses — who keeps what, equalization modifications, asset exclusions — have the highest survival rate. Spousal support waivers are the most frequently challenged and modified, particularly absolute waivers where one spouse later sacrificed their career for the family. A well-structured support clause with defined ranges, SSAG anchoring, and review triggers survives challenge far better than a bare waiver.

The practical takeaway: what makes a prenup enforceable isn't clause sophistication — it's process quality. Full disclosure, independent advice for both parties, adequate time, and fair terms are what courts look for.

How much does a marriage contract cost in Ontario?

Ontario family lawyers charge $300–$500 per hour. A straightforward marriage contract takes 8–15 billable hours per side; complex agreements take longer. Both parties need separate lawyers — that's what Independent Legal Advice means. For the full breakdown of what drives costs, see how much a marriage contract costs in Ontario.

How to get a marriage contract in Ontario

The process has five steps. The order matters — skipping or compressing any step is the most common reason agreements fail.

Step 1: Both parties retain separate Ontario lawyers. Each person hires their own family lawyer independently — not a shared one. This is what "independent" in ILA means.

Step 2: Full financial disclosure. Each party prepares a sworn net worth statement listing all assets, debts, income, and liabilities — with supporting documents: tax returns, property assessments, pension statements, business valuations. This becomes a schedule attached to the final agreement. Completeness is critical. Courts have set aside otherwise sound agreements because of disclosure gaps discovered years later.

Step 3: Negotiate and draft. Terms are discussed and agreed between the parties and their lawyers. A lawyer translates the agreed terms into a properly drafted Ontario marriage contract with the correct FLA section references, a severability clause, and disclosure schedules attached.

Step 4: Independent legal advice for both parties. Each person meets separately with their own lawyer to review the final draft. The lawyer explains what the contract does and doesn't cover, advises on any terms of concern, and confirms the client understands and is signing voluntarily. Both lawyers sign ILA certificates confirming this process occurred. These certificates are the primary evidence courts look for when an agreement is challenged.

Step 5: Sign, witness, and store. Both parties sign in the presence of a witness — who must be an adult and not a party to the contract. Both keep a copy. Store the executed agreement securely. An agreement that cannot be produced at separation is difficult to enforce.

Timing: Start 60–90 days before the wedding, with a minimum of 30 days. Ontario sets no statutory minimum, but agreements signed under last-minute pressure are significantly more vulnerable to challenge on duress grounds. A well-documented timeline is itself a protection.

Frequently Asked Questions

Do I need a lawyer to get a marriage contract in Ontario?

Technically no — Ontario law doesn't require a lawyer to draft a marriage contract. What it requires is proper execution: writing, signatures, and a witness. But Ontario courts consistently treat the absence of Independent Legal Advice as a serious enforceability problem. A 2003 Ontario Superior Court decision stated that upholding an agreement without ILA would be "the exception and not the rule."

Can a marriage contract protect my condo's pre-marriage equity in Ontario?

Yes — and this is one of the most common reasons Ontario property owners get a marriage contract. Under section 4(1) of the Family Law Act, even a home bought entirely before marriage has its full equity subject to equalization at separation if it becomes the matrimonial home. Your pre-marriage equity is not automatically excluded the way other pre-marriage assets can be. A marriage contract is the only way to define how that equity is treated. See how the matrimonial home rule works in Ontario for the full explanation.

Can a marriage contract waive spousal support in Ontario?

Yes, but with limits. Under section 33(4) of the Family Law Act, courts can override a waiver if enforcing it would leave one spouse in serious financial hardship. Blanket lifetime waivers with no conditions are the most vulnerable. A carefully structured clause that references the Spousal Support Advisory Guidelines, sets defined ranges and duration caps, and includes review triggers is substantially harder to set aside — and is what a well-drafted agreement looks like.

What happens to a marriage contract if we have children?

The contract remains in effect, but courts will not enforce any clause predetermining child custody or child support — those are always decided at the time of separation based on the best interests of the child. Significant life changes after signing (birth of children, career interruptions, major shifts in wealth) can also affect whether courts enforce certain support provisions. Reviewing and updating after major life events is strongly recommended.

Can I get a marriage contract after we're already married?

Yes. A postnuptial agreement — signed after the wedding — is valid under Ontario's Family Law Act. The same requirements apply: written, signed, witnessed, with full financial disclosure and ILA. Courts apply slightly more scrutiny because the parties already have existing legal rights when they sign. See postnuptial agreements in Ontario for details.

What's the difference between a marriage contract and a cohabitation agreement in Ontario?

A marriage contract is for people who are married or planning to marry. A cohabitation agreement is for common-law couples living together without marrying. The substantive content is often similar — property, support, debt — but the default law each one modifies is different. Married couples have automatic equalization rights under Part I of the Family Law Act; common-law couples do not. Both are domestic contracts under Part IV of the Act and require the same execution formalities.

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This article provides general information about Ontario family law and does not constitute legal advice. For advice specific to your situation, consult a licensed Ontario lawyer.