Marriage Contracts and Prenuptial Agreements in Ontario

A marriage contract, often called a prenuptial agreement or “prenup”, is a written agreement between two people who are married or plan to marry about what happens to property and support if the marriage ends. Law Wise drafts, negotiates and reviews marriage contracts and cohabitation agreements from its Mississauga office, serving the entire GTA and Ontario.

What a marriage contract is in Ontario

In Ontario the Family Law Act calls it a “marriage contract”: an agreement between spouses, or two people who intend to marry, that sets out their rights and obligations during the marriage, on separation, or on death. The same Act lets unmarried partners make a “cohabitation agreement” covering the same ground, and a cohabitation agreement automatically becomes a marriage contract if the couple later marries.

Without a contract, married spouses in Ontario divide the increase in their wealth during the marriage through “equalization” (our property division page explains how that works), and support is decided under the Family Law Act and the Divorce Act. A marriage contract lets you replace those default rules with terms you have chosen, within the limits described below.

What a marriage contract can cover

• which property stays separate if you separate: a home you owned before the marriage, a business, an inheritance, a family gift;
• how the growth in value of that property is treated, and whether equalization applies at all;
• spousal support: whether it is paid, how much, for how long, or a release of it;
• debts: who is responsible for what;
• what happens on death, which should match your wills (see our wills page);
• ownership of a business and the shares in it, which matters to business partners and lenders as well.

What it cannot do

Two limits are set by the Family Law Act itself. First, a marriage contract cannot take away a spouse’s equal right to live in the matrimonial home or to a say in its sale; a clause that tries to do so is unenforceable, even if the home belongs to one spouse. Second, it cannot decide parenting questions about children, such as decision-making responsibility or parenting time, and a court can disregard any term about child support that falls short of what the Child Support Guidelines would require. Children’s issues are settled when they arise, on the child’s best interests.

Making it enforceable

The formal requirements are short: the contract must be in writing, signed by both of you, and witnessed. What makes the difference years later is how it was made. A court can set aside a marriage contract if one spouse failed to disclose significant assets or debts when it was signed, if a spouse did not understand the nature or consequences of the contract, or on the ordinary grounds for setting aside any contract, such as duress or unconscionability.

Who should consider one

Marriage contracts are common where one or both spouses own a home or a business before the marriage, expect an inheritance, are marrying for a second time with children from the first, have very different incomes or assets, or where parents are contributing to a home purchase and want that contribution protected. They are also used after the wedding; a couple already married can sign one at any time.

If you have been handed a contract to sign

Do not sign it at the kitchen table. Bring it to a lawyer of your own, with the financial information you were given, and ask what you would receive under the ordinary rules compared with what the contract gives you. A short review before the wedding costs far less than a court application years later, and the other spouse benefits too, because a contract that both sides were advised on is far harder to attack.

How Law Wise helps with marriage contracts

• explaining what the default rules would give each of you, so you can decide what to change;
• drafting a marriage contract or cohabitation agreement, including the financial disclosure schedules;
• reviewing a contract prepared by the other spouse’s lawyer and giving independent legal advice;
• converting a cohabitation agreement to a marriage contract, or updating a contract after a business purchase, an inheritance or a child’s birth;
• coordinating the contract with your wills and powers of attorney;
• advising on whether an existing contract can be enforced or set aside on separation.

Your file is handled by a Law Wise lawyer licensed by the Law Society of Ontario. Service is available in English, Urdu, Punjabi and Hindi, and, if you retain the firm, fees are explained and confirmed in writing before work starts.

Common questions about marriage contracts

This page is general legal information for Ontario, current as of 24 October 2026. It is not legal advice and does not create a lawyer-client relationship. For advice about your situation, speak with a lawyer.