- A cohabitation agreement is a domestic contract under Ontario's Family Law Act.
- Even the most carefully written cohabitation agreement cannot override certain rights that belong to your children: - Child support — courts in Ontario will always apply the Child…
Moving in together is a big step — and a joyful one. But in Ontario, common-law partners don't automatically get the same legal protections as married spouses. A cohabitation agreement Ontario couples sign before (or shortly after) moving in together fills that gap. It sets the rules in plain language, while the relationship is healthy and both partners are on the same page.
Think of it less like a breakup plan and more like a shared understanding — the same reason you'd get home insurance before the flood, not after.
What is a cohabitation agreement?
A cohabitation agreement is a domestic contract under Ontario's Family Law Act. It's a written contract between two people who are living together — or who plan to — and who are not married to each other. It spells out each person's rights and obligations during the relationship and if the relationship ends, whether by separation or death.
Common-law partners in Ontario don't share the automatic property-division rules that apply to married spouses. Without an agreement, a partner who contributed to a shared home or business may have no straightforward legal claim to it — and proving a claim in court can be expensive and uncertain. A cohabitation agreement removes that uncertainty before it becomes a problem.
What a cohabitation agreement can cover
A well-drafted agreement is flexible. It can address almost anything related to your financial lives together:
Property ownership and division
- Which property each person owned before moving in, and that it stays theirs
- How property purchased together will be owned (equal shares, unequal shares, or entirely by one partner)
- What happens to the family home if you separate — who has the right to stay, who buys the other out, or when it gets sold
- How any increase in property value is treated
Spousal support
- Whether either partner will pay support to the other if the relationship ends
- A formula or cap for how support is calculated
- Circumstances that would end support (such as either partner remarrying)
Debts
- Which debts belong to which partner
- That one partner won't be responsible for debts the other takes on during the relationship
What happens on death
- How certain assets pass if one partner dies (note: a cohabitation agreement works alongside a will — it doesn't replace one)
Day-to-day financial arrangements
- How you'll split household expenses, mortgage payments, or savings contributions while you're together
What a cohabitation agreement cannot cover
This is important. Even the most carefully written cohabitation agreement cannot override certain rights that belong to your children:
- Child support — courts in Ontario will always apply the Child Support Guidelines, and no agreement can waive a child's right to support
- Decision-making responsibility — formerly called custody; a court will always look at what is in the child's best interests at the time, not what two partners agreed to years earlier
- Parenting time — formerly called access; same principle applies
Any clause that tries to pre-determine these outcomes is unenforceable. A cohabitation agreement is about the two of you — not about binding your children's futures.
Legal requirements for a valid cohabitation agreement in Ontario
Ontario has clear rules. To be legally binding, a cohabitation agreement must be:
- In writing — a verbal agreement has no legal force
- Signed by both parties
- Witnessed — each signature must be witnessed (the witness cannot be one of the two partners)
Independent legal advice: the practical must-have
The law doesn't strictly require that each partner get their own lawyer, but courts take a hard look at agreements where one or both parties didn't receive independent legal advice (ILA). If a challenge ever arises, the absence of ILA is one of the first things a court will consider.
Each partner should have their own lawyer review the agreement and explain what they're giving up and what they're gaining. This step is what gives the agreement its teeth.
What makes a cohabitation agreement challengeable?
A court can set aside a cohabitation agreement — wholly or in part — if:
- Duress or undue influence — one partner was pressured into signing
- Failure to disclose assets — one partner hid or misrepresented their financial situation before signing
- Unconscionable terms — the agreement was so one-sided that enforcing it would be fundamentally unfair
- No independent legal advice — especially if the disadvantaged partner didn't understand what they were agreeing to
- Fraud or misrepresentation — one partner provided false information
This is why both full financial disclosure and independent legal advice aren't just formalities — they're the foundation that makes the agreement stick.
If you get married later, the agreement upgrades automatically
This is a detail many people miss: under Ontario's Family Law Act, a cohabitation agreement that was valid when you signed it automatically becomes a marriage contract if you and your partner later marry. You don't need to sign a new document — the same agreement continues to govern your rights and obligations as a married couple.
That said, your circumstances will likely have changed by the time you marry. It's worth having a lawyer review the agreement at that point to confirm it still reflects what you both intend.
Timing matters: sign before you move in
The best time to sign a cohabitation agreement is before you move in together — or very shortly after. Here's why timing matters:
- Once partners are already living together, courts sometimes scrutinize whether there was real pressure to sign quickly
- Pre-move-in agreements are easier to negotiate calmly, without the urgency of an imminent move date
- If one partner has already made financial commitments — selling their home, leaving a job — they're in a weaker negotiating position
Starting the conversation early isn't pessimistic. It's a sign that both partners respect each other enough to be honest about their finances.
The cost comparison: agreement now versus litigation later
A cohabitation agreement typically costs a fraction of what a disputed separation costs. Family litigation in Ontario — court applications, motions, discoveries, trials — can run into tens of thousands of dollars and take years. The emotional cost on top of that is real and significant.
A flat-fee cohabitation agreement, reviewed by independent counsel for each partner, is one of the more straightforward family law matters. The cost is predictable. The timeline is short. And it protects both partners — not just the one with more assets.
Frequently asked questions
Do common-law couples have the same property rights as married couples in Ontario?
No. In Ontario, common-law partners (as of writing — verify current rules) are generally not entitled to an automatic equal division of property the way married spouses are under the Family Law Act. Without a cohabitation agreement or a successful court claim, each partner typically keeps what is in their own name.
How long do you have to live together to be common-law in Ontario?
For most purposes under Ontario law, partners who have cohabited continuously for three years — or who are in a relationship of some permanence and have a child together — are treated as spouses for spousal support purposes (as of writing — verify current rules for your specific situation). Property division rules are separate and do not automatically apply.
Can we write our own cohabitation agreement without a lawyer?
Legally, nothing stops you from drafting your own agreement. In practice, homemade agreements are far more likely to be challenged and set aside — especially if one partner later argues they didn't understand what they signed, or that key assets weren't disclosed. For an agreement that holds up, each partner needs independent legal advice.
What happens to our cohabitation agreement if we separate and then get back together?
It depends on what the agreement says and the circumstances of the reconciliation. Separating and resuming the relationship may or may not void the agreement — courts look at the parties' intent. If you reconcile after a separation, it's worth reviewing the agreement with your lawyer to confirm how it applies going forward.
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