Separation Agreements in Ontario

A separation agreement is a written contract that settles parenting, support and property when a relationship ends, without asking a judge to decide. Law Wise prepares, negotiates and reviews separation agreements, marriage contracts (prenuptial agreements) and cohabitation agreements from its Mississauga office, serving the entire GTA and Ontario.

Domestic agreements in Ontario

Ontario’s Family Law Act calls these agreements domestic contracts. There are three main kinds:

• Separation agreement. Made by two people who lived together, married or not, and are now living separate and apart. It can deal with property, support, the children’s education and upbringing, and decision-making responsibility and parenting time.
• Marriage contract. Often called a prenuptial or pre-nuptial agreement. It is made by two people who are married or intend to marry, and can deal with property and support during the marriage, on separation, on divorce or on death.
• Cohabitation agreement. Made by two people who live together or plan to, and are not married to each other. If they later marry each other, the agreement is treated as a marriage contract.

What a separation agreement usually covers

• where the children live and how parenting time is shared
• who makes major decisions for the children
• child support, including special expenses and a yearly exchange of income information
• spousal support: the amount, how long it lasts and whether it can be reviewed
• division of property and debts, including any equalization payment
• the family home: who stays, whether it is sold and when
• pensions, insurance and benefits
• how future disagreements will be resolved

A separation agreement stands on its own whether or not you later divorce. If you are married, the divorce is a separate court step, and a signed agreement usually makes it a simple one. More detail on each topic is on our pages about parenting, child support, spousal support and property division.

Marriage contracts and cohabitation agreements

Couples make these agreements before or during a relationship so that they, and not a formula applied years later, decide how property and support will be handled if the relationship ends. Common reasons include:

• protecting property owned before the relationship
• keeping a business or professional practice out of a later property claim
• providing for children from an earlier relationship
• planning for an expected gift or inheritance

The law sets limits. A marriage contract or cohabitation agreement cannot decide in advance who will have decision-making responsibility or parenting time for children. A marriage contract also cannot limit a spouse’s rights in the matrimonial home under Part II of the Family Law Act, such as the right to possession.

Unmarried partners do not share property under Ontario’s equalization rules, so a cohabitation agreement is often the way they set their own rules for property.

What makes an agreement enforceable

A domestic contract must be in writing, signed by the parties and witnessed. If it is not, it cannot be enforced. Even a properly signed agreement can be set aside by a court, in whole or in part, if:

• a party did not disclose significant assets, debts or other liabilities that existed when the agreement was made
• a party did not understand the nature or consequences of the agreement
• the law of contract otherwise allows it, for example where there was duress or misrepresentation

These grounds apply even if the agreement says they do not. Terms about children and support are also open to review:

• A court can disregard terms about parenting, education or upbringing where that is in the best interests of the child.
• A court can disregard a child support term that is unreasonable having regard to the child support guidelines.
• A court can set aside a support term, or a waiver of support, in limited cases, for example where it results in unconscionable circumstances.

Filing and enforcing an agreement

A party can file a domestic contract with the Ontario Court of Justice or the Family Court of the Superior Court of Justice, together with an affidavit stating that the agreement is in effect and has not been set aside or changed. Once it is filed, its support terms can be enforced, and changed, as if they were a court order. See FRO and default hearings for how support is collected.

If you have been handed an agreement to sign

The lawyer who prepared the draft acts for your spouse or partner, not for you. Before you sign, have your own lawyer review it. Law Wise reviews draft agreements, explains each term in plain language, and tells you what is usual, what is missing and what you may want to change.

Changing an agreement later

Circumstances change: incomes rise and fall, children grow and people move. A well-drafted agreement says how it can be reviewed or changed. If yours does not, the two of you can sign an amending agreement, which must also be in writing, signed and witnessed, and the support terms of a filed agreement can be changed by a court.

How Law Wise helps with domestic agreements

• explaining your rights and obligations before you negotiate
• gathering and exchanging financial disclosure
• negotiating terms with the other side or their lawyer
• drafting a separation agreement, marriage contract or cohabitation agreement
• giving independent legal advice on an agreement prepared by someone else
• filing the agreement with the court where that is needed

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 separation agreements

This page is general legal information for Ontario, current as of 10 October 2026. It is not legal advice and does not create a lawyer-client relationship. For advice about your situation, please speak with a lawyer.