Cohabitation Agreements in Ontario: What Common-Law Partners Need to Know

Millions of Canadians live in common-law relationships, and a significant number of them assume they have the same legal rights as married spouses. In Ontario, that assumption is largely incorrect — and the gap between expectation and reality can be financially devastating when a relationship ends. A cohabitation agreement is the legal tool that lets common-law partners define their rights and obligations in advance, on their own terms.

What "Common-Law" Actually Means in Ontario

Ontario law does not use the term "common-law" uniformly. Different statutes define the relevant relationship differently:

• Family Law Act (property): For property-division purposes, only legally married spouses have rights under Ontario's equalization regime. Common-law partners — regardless of how long they have lived together — do not have an automatic right to share in each other's property at the end of the relationship.
• Family Law Act (support): Common-law partners who have cohabited continuously for three or more years, or who are in a relationship of some permanence and are the natural or adoptive parents of a child together, may owe each other spousal support.
• Succession Law Reform Act (inheritance): Common-law partners have no automatic right to inherit under intestacy law unless they are a "spouse" under the definition relevant to estates, which in Ontario generally means a married spouse. Common-law partners who are not married do not inherit by default.
• Benefits and pensions: Many government programs and employment benefits use their own definitions of "spouse" or "partner." Some recognize common-law relationships after a defined cohabitation period; others require marriage.

The takeaway: being common-law in Ontario gives you some protections (particularly for spousal support after three years, and parental rights for shared children) but not the full suite of rights that married spouses have.

What Is a Cohabitation Agreement?

A cohabitation agreement is a domestic contract between two people who are living together (or intend to live together) outside of marriage. Under Ontario's Family Law Act, domestic contracts are binding agreements that can:

• Define how property will be divided if the relationship ends
• Address who owns the home they share (and what happens to it on separation)
• Set out financial support obligations during and after the relationship
• Protect assets brought into the relationship or inherited during it
• Confirm that one party is not entitled to an interest in the other's business
• Address debts and liabilities
• Include provisions for children (though child support and parenting arrangements remain subject to court oversight regardless of what a contract says)

What it cannot do

A cohabitation agreement cannot:

• Limit a court's ability to order child support in the child's best interests
• Validly restrict court oversight of parenting arrangements

Why Common-Law Partners in Ontario Should Have One

Without a cohabitation agreement, the default legal position for common-law partners in Ontario is:

Property: No automatic sharing. If you separate after 10 years and your partner owns the house in their name alone, you have no Family Law Act right to equalization. You may have an unjust enrichment or constructive trust claim if you contributed to the property — but these are litigation claims that are expensive, uncertain, and stressful to pursue.

Support: Possible after 3 years of cohabitation, but the amount and duration are discretionary and litigable.

Debt: You are generally not liable for your partner's debts — but joint debts are a shared responsibility regardless of a cohabitation agreement.

Death: Without a will, your common-law partner may receive nothing from your estate. A cohabitation agreement addresses asset division on separation; your will addresses what happens on death.

A cohabitation agreement — combined with updated wills and beneficiary designations — gives common-law partners certainty and control.

Automatic Conversion: When a Cohabitation Agreement Becomes a Marriage Contract

Under Ontario's Family Law Act, if partners who have a cohabitation agreement later marry each other, the agreement automatically becomes a marriage contract and continues in effect, unless the agreement says otherwise. This is a practical benefit — you don't have to redo the agreement if you marry, unless your circumstances have changed significantly.

Requirements for a Valid Cohabitation Agreement

To be enforceable under Ontario's Family Law Act, a cohabitation agreement must:

1. Be in writing
2. Be signed by both parties
3. Be witnessed

The Act also permits courts to set aside a domestic contract — or part of it — if:

• A party did not disclose significant assets or debts before signing
• A party did not understand the nature or consequences of the contract
• The contract was unconscionable (grossly unfair in a way that shocks the conscience)

To guard against these challenges, both parties should obtain independent legal advice before signing and should each disclose their financial situation fully. This is not a legal requirement, but it significantly strengthens the agreement's enforceability.

Registered Domestic Partnerships (Alberta vs. Ontario)

Note that Ontario does not have a "Adult Interdependent Partner" registry like Alberta does — that's a different province's system. Ontario common-law partners rely on the Family Law Act domestic contract regime rather than any formal registration system. Some Ontarians informally use the term "adult interdependent partner" after seeing it used in Alberta or in federal contexts, but it has no specific legal meaning under Ontario provincial law.

Frequently asked questions