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Do You Need a Cohabitation Agreement in Ontario?

Many couples in Ontario live together for years without marrying — sharing a home, bills, sometimes children — and assume the law treats them much like married spouses. For property, it mostly does not. This guide explains where unmarried partners stand, and what a cohabitation agreement can change.

What “common-law” means in Ontario

Ontario does not register common-law relationships, and there is no single moment when a couple becomes “common-law” for every purpose — different laws use different tests. For spousal support under Ontario’s Family Law Act, an unmarried partner counts as a “spouse” after the couple has lived together continuously for at least three years, or after they have lived together in a relationship of some permanence and are the parents of a child together — often summarized as about one year together with a child. Tax law, pensions and federal benefits each apply their own definitions, on their own timelines.

The big difference from marriage: property

Marriage changes the property rules automatically. When married spouses separate in Ontario, the law provides for an equalization of net family property — a calculation designed to share the growth in the couple’s wealth during the marriage, with defined exceptions such as certain gifts and inheritances. Married spouses also have special rights in the matrimonial home, whoever owns it.

No equivalent system exists for unmarried partners. For common-law couples, property generally belongs to the person who owns it: the name on title, the account holder, the purchaser. A partner who contributed to property owned by the other — paying toward a mortgage, or renovating a house, for example — may be left to argue a claim based on unjust enrichment or a “joint family venture.” Those claims mean court, cost and uncertainty, with no guaranteed result. And because the matrimonial home protections apply to married spouses, an unmarried partner has no automatic right to remain in a home owned by the other partner.

What a cohabitation agreement can cover

A cohabitation agreement is a domestic contract under the Family Law Act in which an unmarried couple records their own arrangements, instead of leaving everything to default rules and future court claims. It can set out:

• Who owns what, and in what shares — including a home the couple buys together
• How property would be divided if the relationship ends
• Responsibility for debts and for household expenses while living together
• What happens to the home — who may live there, and how a buyout would be valued
• Whether spousal support would be paid if the relationship ends, and on what basis, within the limits the law allows
• Arrangements for pets and jointly owned belongings

There are limits. A cohabitation agreement cannot settle parenting arrangements or child support in advance in a way that binds a court: those decisions are made according to a child’s best interests at the time they arise, and child support follows the Child Support Guidelines.

Writing, witnesses, disclosure and advice

To be enforceable, a cohabitation agreement must be in writing, signed by both partners, and witnessed. Two further ingredients give an agreement its strength. The first is financial disclosure: each partner shares a fair picture of their income, assets and debts before signing, because Ontario courts can set aside a domestic contract where significant assets or debts were not disclosed, where a partner did not understand the agreement, or where ordinary contract law would undo it. The second is independent legal advice — each partner reviewing the agreement with their own lawyer. It is one of the clearest signals that both sides understood what they were signing.

If the couple later marries

Marriage changes the default property rules, but a cohabitation agreement can plan for that: Ontario law allows the agreement itself to state that it continues as a marriage contract if the couple marries. Couples who marry without that provision often revisit their arrangements and sign a marriage contract instead, so that the rules they chose are not replaced by defaults they never looked at.

When couples usually write one

The common triggers are practical ones: buying a home together, one partner moving into a home the other already owns, a large difference in income, assets or debts, children from earlier relationships, or a family business one partner is part of. The thread running through all of them is not a lack of trust. It is that the default rules were not designed with their situation in mind — and a short written agreement costs far less than a court claim about what was really intended years later.