- Ontario's Family Law Act treats a marriage contract and a cohabitation agreement as two kinds of domestic contract, and a cohabitation agreement is deemed a marriage contract if the parties marry each other.
- Married spouses have default property-equalization rules, while Ontario's property-division rules do not require unmarried couples to split property acquired while living together.
- Neither contract can settle decision-making responsibility or parenting time, and a court can set aside terms in certain circumstances.
- Spousal support rules can reach unmarried partners in some cases.
If you and your partner are deciding whether to marry or stay common-law, the legal differences matter. Ontario treats property very differently depending on whether you are married, and a written contract can change the result either way.
This article explains how the two main contracts work, how the default rules differ, and what they can and cannot cover. It is general information, and a lawyer can confirm how it applies to you.
Two names for two kinds of domestic contract
Ontario's Family Law Act defines a domestic contract as a marriage contract, separation agreement, cohabitation agreement, paternity agreement or family arbitration agreement. 'Prenup' and 'prenuptial agreement' are informal names, and the Act uses the term marriage contract.
Two people who are married to each other or intend to marry may make a marriage contract. It is not limited to the time before the wedding, because people who are already married may also make one. Common-law partners can set property rights by a cohabitation agreement.
If the parties to a cohabitation agreement later marry each other, the agreement is deemed to be a marriage contract.
How property works with and without a contract
For married spouses, the default rule is equalization. On divorce, nullity or separation with no reasonable prospect of resuming cohabitation, the spouse with the lesser net family property is entitled to one-half of the difference. Certain property, such as gifts or inheritances from a third person after the date of marriage, is excluded even without a contract.
Ontario's property-division rules do not require unmarried couples to split property acquired while living together. A cohabitation agreement is how common-law partners can set their own property rights.
A married couple can contract out of equalization. Property the spouses have agreed by a domestic contract is not to be included is excluded from net family property. The matrimonial home is a notable case: without a contract, its full value must generally be shared, even if it was owned before marriage, gifted or inherited.
Support, children and the matrimonial home
Both kinds of contract can cover support, property division and who moves out of the home. They cannot say who will have decision-making responsibility or parenting time. A court may also disregard a term about a child's education, moral training, decision-making responsibility or parenting time if doing so is in the child's best interests.
Child support is also protected. A court may disregard a contract provision on child support if it is unreasonable having regard to the child support guidelines.
For spousal support, a court may set aside a support provision or waiver if it results in unconscionable circumstances, if it involves a dependant who qualifies for public support, or if support under the contract is in default. For support under Part III, 'spouse' includes unmarried partners who cohabited continuously for at least three years, or who are in a relationship of some permanence and are the parents of a child.
A term in a marriage contract that tries to limit a spouse's rights under Part II (Matrimonial Home) is unenforceable.
Which contract fits your situation
| Situation | Contract that generally fits |
|---|---|
| Planning to marry, or already married | Marriage contract |
| Staying common-law | Cohabitation agreement |
| Common-law now, may marry later | Cohabitation agreement, deemed a marriage contract on marriage |
Whichever you choose, it must be in writing, signed by the parties and witnessed, or it is unenforceable.
What to do next
- Decide together whether you plan to marry, stay common-law, or keep both options open.
- List your assets, debts and other liabilities, because failing to disclose significant ones can lead a court to set a contract aside.
- Exchange financial information and each speak to a different lawyer before signing.
- Sign in writing in front of a witness, who also signs.
- Do not sign under pressure, since a court can set a contract aside on general contract law grounds.
Frequently asked questions
Do we need a lawyer to make a valid contract?
The formal requirements are writing, signatures and a witness, and a lawyer is not one of them. Ontario's government still advises that each partner speak to a different lawyer and exchange financial information before signing.
Can a contract decide parenting time?
No. These contracts cannot say who will have decision-making responsibility or parenting time.
When can an Ontario court disregard or set aside parts of my domestic contract?
On application, a court may set aside a contract or a provision if a party failed to disclose significant assets or debts, did not understand its nature or consequences, or on other contract law grounds. A clause cannot remove that power.
Do common-law partners split property automatically?
No. Ontario's property-division rules do not require unmarried couples to split property acquired while living together. A cohabitation agreement can set property rights.
Sources
- Family Law Act, R.S.O. 1990, c. F.3 (e-Laws), s. 51 — Ontario e-Laws
- Ontario.ca – Dividing property when a marriage or common law relationship ends — ontario.ca
Links go to official government, court and regulator pages. The law changes — confirm you are reading the current version.
This is a family law question
Start a file online — flat, published fees, reviewed by a licensed lawyer before a dollar is owed.