Marriage Contracts and Cohabitation Agreements: What They Can and Can’t Do for Your Home in Ontario

Four couples, four legal positions. Where you stand when you sign, and where you stand when it ends, decides which clauses about the house will hold.

I’m Arthur Zhao, a broker with AZ Real Estate Partners. A version of this conversation comes up when one partner already owns a place and the other is about to give notice on a lease. They are moving in together this spring, a wedding is pencilled in for next year, and one of them has heard that a prenup protects the house. The question underneath is more precise: which document, signed when, does what?

Ontario’s Family Law Act answers that differently depending on where a couple stands. Below are four situations: planning to marry when one of you already owns, already married, living together with no plan to marry, and living together first and marrying later. For each I set out what an agreement can do for the home and where the Act stops it. I am not a lawyer, and this is not a substitute for a family lawyer’s advice; the aim is to know which questions to bring to one.

Situation 1: You are getting married and one of you already owns the home

This is what most people mean by a prenup. The Act’s term is marriage contract. Section 52(1) lets two people who are married to each other or intend to marry agree on their rights on separation, on annulment or dissolution of the marriage, or on death, including “ownership in or division of property” (s.52(1)(a)).

Why owners look at one. When a marriage ends, the spouse with the smaller net family property is entitled to half the difference between the two (s.5(1)). Normally you deduct what you owned on the wedding day, but the s.4(1) definition carves out a matrimonial home, so a place you owned before the wedding and then live in together generally gets no deduction for its pre-marriage value. The related piece on the matrimonial home covers that rule; here it is simply the reason the question arises.

What the contract can do. According to the Family Law Act (2026 consolidation), s.4(2) lists property whose value does not form part of net family property, and paragraph 6 reads: “Property that the spouses have agreed by a domestic contract is not to be included in the spouse’s net family property.” Paragraphs 1 and 5 on the same list carry the words “other than a matrimonial home”. Paragraph 6 does not. On the text, then, an agreement can address the home’s value. Section 2(10) adds that a domestic contract dealing with a matter the Act also deals with prevails “unless this Act provides otherwise.” Whether a given clause holds up in a given dispute is for a court; the text does not promise an outcome.

What it cannot do. The “provides otherwise” is s.52(2): a provision in a marriage contract “purporting to limit a spouse’s rights under Part II (Matrimonial Home) is unenforceable.” Part II is where occupancy and consent live. Property counts as a matrimonial home under s.18(1) if a person has an interest in it and the couple ordinarily occupy it as their family residence, so sole title does not keep it out. Section 19(1) gives both spouses an equal right to possession; s.19(2) explains how that works when only one spouse owns: the right is personal as against the owner and ends when they cease to be spouses, unless a separation agreement or court order provides otherwise. Section 21(1) bars either spouse from disposing of or encumbering the home without the other joining in or consenting, subject to listed exceptions. A pre-wedding clause written to switch those off is a clause the Act says will not be enforced.

Situation 2: You are already married and want to sign now

Signing after the wedding does not produce a different kind of document. Section 52(1) covers two people “who are married to each other or intend to marry”, so an agreement signed in year five of a marriage is a marriage contract just as one signed a month before the ceremony. The same tools and the same limit apply: you can agree how the home is owned or divided and how property is treated in net family property (s.4(2) paragraph 6), and you cannot contract out of Part II (s.52(2)).

Two things are different in practice. First, if the couple already lives there, the home is already a matrimonial home under s.18(1), and s.21(1) is already working on it. That section reaches further than a sale: no spouse shall “dispose of or encumber” an interest in a matrimonial home, so a refinance or a new mortgage is caught as well. A contract signed later does not change that, because s.52(2) keeps Part II out of its reach.

Second, disclosure. Under s.56(4)(a) a court may set aside a domestic contract, or a provision in it, if a party failed to disclose significant assets, or significant debts or other liabilities, “existing when the domestic contract was made.” After some years of marriage that list can be longer: the mortgage balance as it stands today, other property, investments. Section 56(7) says this power applies despite any agreement to the contrary, so a clause waiving disclosure does not remove it.

Releasing Part II rights takes a separation agreement. Section 21(1)(b) allows a disposition where “the other spouse has released all rights under this Part by a separation agreement.” Section 54 makes a separation agreement a document for two people who “cohabited and are living separate and apart”, so a couple still living together cannot sign one in advance.

Situation 3: You live together and don’t plan to marry

Here the starting point flips. Section 1(1) defines “spouse” as either of two people who are married to each other, or who entered in good faith into a marriage that is void or voidable. Part I (net family property and equalization) and Part II (the matrimonial home) use that definition. The wider definition in s.29, which takes in partners who have cohabited continuously for at least three years, or who are in a relationship of some permanence and are the parents of a child, opens with “In this Part”, and that Part is Part III, support.

My reading, which is an inference from those definitions rather than a quoted rule: partners who are not married have no statutory equalization of net family property and no Part II possession or consent rights in the home. A cohabitation agreement, then, is not adjusting a default the Act would otherwise impose. It is where you write the property terms yourselves. Section 53(1) lets two people “who are cohabiting or intend to cohabit and who are not married to each other” agree on their rights during cohabitation, on ceasing to cohabit, or on death, including “ownership in or division of property” (s.53(1)(a)).

For a home, that turns into practical questions: whose name goes on title, how each person’s contribution to the down payment or the mortgage is treated, and what happens to the home if you part. How co-owners hold title, as joint tenants or tenants in common, is a separate decision with its own consequences (see the related reading). Support runs on a different track from property: if the s.29 test is met, Part III support rules can apply, and s.53(1)(b) lets the agreement deal with support obligations. How a court treats a support term is outside this article.

Married or living together: where the rules for the home come from

Situation 4: You signed a cohabitation agreement, then married each other

Section 53(2) is one sentence: “If the parties to a cohabitation agreement marry each other, the agreement shall be deemed to be a marriage contract.” No re-signing is needed for it to carry into the marriage. What changes is the set of rules it is read against.

Put the two subsections side by side. Once the agreement is deemed a marriage contract, s.52(2) applies to it, so a clause limiting a spouse’s Part II rights is unenforceable from then on. A term that worked as a plain ownership arrangement while you were unmarried, such as one partner keeping sole control over the home they own, can run into the equal right of possession in s.19(1) and the consent rule in s.21(1) once you are spouses. This is my reading of how the two provisions interact; the Act does not set out that sequence in its own words.

The value side carries over more cleanly. Section 51 defines “domestic contract” to include a cohabitation agreement, and s.4(2) paragraph 6 excludes property the spouses “have agreed by a domestic contract” is not to be included in net family property. The catch is practical. An agreement written by two people who did not expect to marry may say nothing about net family property, because when it was signed there was no equalization to plan around. Whether yours does is worth reading with your lawyer before the wedding rather than after a separation.

What any of these agreements needs in order to stand

Whichever situation you are in, the form rules are short. Under s.55(1), a domestic contract, and an agreement to amend or rescind one, is unenforceable “unless made in writing, signed by the parties and witnessed.” A minor can enter one only subject to court approval, which may come before or after signing (s.55(2)).

Beyond form, s.56(4) lets a court set aside the contract or a provision in it if a party failed to disclose significant assets or debts, if a party “did not understand the nature or consequences” of the contract, or otherwise in accordance with the law of contract. The Act does not list separate legal advice for each person among the s.55 requirements. On my reading it bears on the understanding question in s.56(4)(b), but that is an inference about evidence, not a statutory rule; your lawyer is the one to say how they want to handle it.

Before you sign: a working list

Grouped by the kind of risk each item guards against, not by when you do it.