Marriage Contracts (Prenuptial Agreements) in Ontario

What Is a Prenuptial Agreement in Ontario?#

A marriage contract, also known as a prenuptial agreement or prenup, lets a couple getting married in Ontario protect assets and clarify their financial expectations in the event of separation. “Marriage contract” is the legal term used in the Family Law Act (FLA), Part IV. “Prenuptial agreement” and “prenup” are common in everyday language, but Ontario law does not use them.

A marriage contract is a type of domestic contract that two people who are married or planning to marry can enter into. It sets out how property, debts, and support obligations will be handled during the marriage and on separation or death, instead of leaving those issues to the default rules in the Act. For couples who live together without marrying, the parallel document is a cohabitation agreement, and the rules start from a different place entirely; our guide to common law in Ontario covers them.

Marriage contracts are governed by FLA sections 51 to 55, which define the contract, set out what it can cover, and impose the formal requirements: a domestic contract is unenforceable unless it is in writing, signed by the parties, and witnessed (s. 55(1)). The grounds for setting aside a domestic contract appear in section 56, and those provisions apply equally to marriage contracts, cohabitation agreements (s. 53), and separation agreements (s. 54).

What a Marriage Contract Can and Cannot Include#

Clients frequently ask what a marriage contract can actually cover, as Ontario’s restrictions differ from other provinces. The FLA sets clear boundaries in section 52.

The restriction on the matrimonial home is an Ontario-specific rule that many people do not know exists until they sit down with a lawyer. Under the FLA, both spouses have an equal right to possession of the matrimonial home, regardless of who holds title. A marriage contract cannot contract out of this right (s. 52(2)). Many people assume a prenup can keep the family home with the spouse who owned it before the marriage. A marriage contract can address how the home’s ownership and value are divided, but it cannot limit either spouse’s possessory rights under Part II of the FLA.

The restriction on decision-making responsibility and parenting time (s. 52(1)(c)) reflects the principle that a court must determine parenting arrangements based on the best interests of the child at the time of separation. That requires an assessment of the child’s current circumstances, not reliance on what two people agreed to years earlier. Even the education and moral training terms a contract may include are not final: under s. 56(1), a court may disregard any provision of a domestic contract about a child’s education, moral training, decision-making responsibility or parenting time where doing so is in the child’s best interests.

How a Court Can Set Aside a Marriage Contract#

A marriage contract is not automatically enforceable just because both parties signed it in the proper form. Under FLA s. 56(4), a court retains the discretion to set aside a domestic contract or any provision in it if:

1. A party failed to disclose significant assets, debts, or other liabilities existing at the time the contract was made.
2. A party did not understand the nature or consequences of the contract.
3. Otherwise in accordance with the law of contract, meaning the general contract defences (duress, undue influence, unconscionability, misrepresentation) can defeat a marriage contract just as they can any other contract.

The Supreme Court of Canada set out the framework for weighing a spousal-support agreement in a Divorce Act application in Miglin v. Miglin, 2003 SCC 24 at paras 80-91. The Court set out a two-stage test. First, the court looks at the circumstances in which the agreement was negotiated and executed (oppression, pressure, vulnerability, the degree of professional advice) and at whether the agreement’s substance substantially complied with the legislation when it was made. Second, it asks whether the agreement still reflects the parties’ original intentions at the time of the application, or whether circumstances have moved so far outside what the parties could reasonably have anticipated that holding them to the bargain cannot be condoned. Miglin arose from a separation agreement under the Divorce Act, but Ontario courts apply its procedural-integrity principles to marriage contracts as well.

At the appellate level, LeVan v. LeVan, 2008 ONCA 388 shows what actually sinks a marriage contract. The Court of Appeal confirmed that the s. 56(4) analysis is a two-step process: first, has the party seeking to set aside the contract established one of the listed grounds; second, should the court exercise its discretion to set the contract aside (at para 51). It upheld the trial decision setting aside a marriage contract where the husband had failed to disclose significant assets and the wife had signed an extremely unfair agreement without meaningful independent legal advice.

The flip side is Hartshorne v. Hartshorne, 2004 SCC 22, a British Columbia case decided under that province’s family property legislation rather than Ontario’s FLA, where the Supreme Court enforced a marriage agreement even though the wife’s own lawyer had advised her it was grossly unfair. She had independent legal advice, understood the terms, and signed anyway. The Court held her to the bargain. It illustrates the underlying principle rather than binding Ontario courts. Taken together, the cases put process first: where disclosure was full, the advice was real, and nobody was pressured, an uneven deal may still be upheld, depending on the full circumstances. But outcome is not irrelevant: the second stage of Miglin asks whether the agreement still substantially complies with the Divorce Act’s objectives at the time of enforcement, and FLA s. 33(4) lets a court override a support term that produces an unconscionable result. Where the process was compromised, even a reasonable-looking deal is vulnerable.

For a recent Ontario example on the enforcement side, in Singh v. Khalill, 2024 ONCA 909 the Court of Appeal upheld a marriage contract found valid at first instance and dismissed the appeal (at paras 1-2).

What Makes a Prenup Enforceable in Ontario#

Based on the FLA and case law, a marriage contract is most likely to withstand a court challenge when these conditions are met:

Full financial disclosure. Both parties must provide a complete and honest picture of their income, assets, and debts, because full disclosure is one of the most important factors in enforceability. Incomplete disclosure is an express statutory ground for setting aside a contract.

Independent legal advice (ILA). Each party should retain their own lawyer. The lawyer reviews the agreement, explains its effects, and signs a certificate confirming the client understood what they were signing. While ILA is not technically mandatory under the FLA, a contract signed without it is far more vulnerable to challenge.

No pressure or duress. Signing a prenup the night before the wedding, or after wedding deposits are non-refundable, can give rise to a credible argument that one party was under undue pressure. Parties should negotiate and sign the agreement well in advance of the ceremony to avoid any inference of coercion.

Clear and specific terms. Vague language creates disputes. The contract should state what property is excluded from equalization, what happens with the matrimonial home’s value (keeping in mind that possession rights cannot be waived), and how spousal support is addressed.

Reasonable terms. An agreement with very harsh terms may face a stronger challenge, especially if the process leading to it was also flawed.

What If the Wedding Is Only Weeks Away?#

A marriage contract does not have to be signed before the wedding. FLA s. 52(1) allows two people who are married to each other, or who intend to marry, to enter into one, so an agreement signed after the ceremony is still a marriage contract with the same scope and the same formal requirements.

Timing matters because the circumstances in which a contract was signed are part of what a court looks at if it is later challenged. Financial disclosure, valuation of a business or a property, negotiation between two lawyers, and independent legal advice all take time. When that work is squeezed into the weeks before a wedding, it can be easier for a spouse to argue later that they felt pressured or did not fully understand the terms, even if the agreement is otherwise sound.

When a client comes to us with the wedding close, our recommendation is often to let the wedding go ahead and sign the marriage contract afterward, once the dust has settled. That does not mean the work has to wait. The disclosure, the negotiation, and the terms themselves can all be worked out before the wedding. It is the signing that is better left until after. The agreement can still address property each spouse owned on the date of marriage, the treatment of the matrimonial home’s value, and spousal support, and a contract signed without a wedding date looming leaves less room for the argument that someone signed under pressure.

There are two cautions that come with this approach. The first is that the default rules in the FLA govern until the contract is signed, so if the marriage ended in that window, property and support would be decided under the Act. The second is that an agreement can easily drift once the wedding is over, so the terms should be settled beforehand and a signing date set for soon after the ceremony.

A Practical Example#

Consider Amir and Priya. Amir owns a home worth $850,000 and has a family business valued at $1.2 million. Priya is a teacher earning $75,000 per year. They plan to marry in eight months.

They decide to enter into a marriage contract. The process looks something like this:

1. They discuss their goals together informally.
2. Each retains their own family lawyer.
3. Both complete sworn financial statements listing assets, debts, income, and liabilities.
4. Amir’s lawyer drafts the agreement. It proposes that Amir’s business and its growth remain excluded from equalization, but that the increase in value of the home during the marriage will be shared.
5. Priya’s lawyer reviews the draft, requests changes, and negotiates terms for spousal support if the marriage lasts more than five years.
6. Both sign the agreement four months before the wedding. Each lawyer signs a certificate of independent legal advice.

The agreement does not address decision-making responsibility or parenting time for future children, because the FLA does not allow that. It does not attempt to waive Priya’s right to live in the matrimonial home. The home Amir currently owns will likely become the matrimonial home once they marry and live there, and both will have a right to possession regardless of what the contract says.

This process takes time and money, but it produces a much stronger agreement if the marriage later breaks down.

How Much Does a Prenup Cost in Ontario?#

The cost depends on how complex the parties’ finances are and how much negotiation is needed. The figures below are general ranges drawn from our experience rather than fixed quotes, and they vary with the disclosure, valuation, and negotiation involved. They also exclude HST and disbursements.

For a straightforward agreement where both parties are broadly aligned, legal fees are often in the range of $5,000 to $7,500 per person. That covers the financial disclosure, drafting or reviewing the agreement, negotiation, and the ILA certificate.

For complex situations involving business interests, multiple properties, or trusts, fees can reach $10,000 to $15,000 or more per person.

Because each party retains their own independent counsel, the total cost for the couple is roughly double the per-person estimate.

The cost of a separation agreement or litigation over property division if a marriage breaks down without a contract often exceeds the cost of a well-drafted marriage contract.

Common Prenup Mistakes to Avoid#

Signing too close to the wedding. I find that this comes up regularly. If a contract is presented days before the ceremony, a court may find that the other party was under pressure to sign. If the date is already close, it is usually better to sign after the wedding instead.

Incomplete financial disclosure. Leaving out assets, undervaluing property, or failing to disclose debts can be fatal to a marriage contract, because these omissions provide precisely the basis that section 56(4) contemplates for setting aside the agreement. Disclosure must be thorough and current as of the date of execution.

Skipping independent legal advice. Without ILA, a party can subsequently argue they did not understand the nature or consequences of the agreement, which is a recognized statutory ground for setting the contract aside. Paying for independent advice up front is generally far less costly than litigating the contract’s validity after separation.

Trying to address children’s issues. A marriage contract cannot determine future decision-making responsibility or parenting time; a court decides those issues based on the child’s best interests at the time, regardless of what the contract says.

Assuming the matrimonial home is protected. This is the misconception I see most often. People assume that a home one spouse owned before the wedding stays with that spouse if the marriage ends. Ontario law starts from the opposite position and gives the other spouse rights in that home. If the property is still the matrimonial home when the couple separates, both spouses have an equal right to possession regardless of whose name is on title, and the owner gets no deduction for the home’s date-of-marriage value in the equalization calculation, unlike other property brought into the marriage (s. 4(1)). The non-owning spouse ends up sharing in the home’s full value. If you own a property and plan to marry, a marriage contract is essential. It can set how the home’s value is treated on separation, although it cannot remove the other spouse’s right to possession.

Frequently Asked Questions#

If you are considering a marriage contract, or have questions about an existing prenuptial or cohabitation agreement, contact Krol & Krol for a consultation.