- A court may set aside a domestic contract or a provision in it if a party failed to disclose significant assets or debts, did not understand its nature or consequences, or on contract-law grounds such as duress.
- The court uses two stages: you first prove a listed ground, then the court decides in its discretion whether to set the agreement aside.
- Breaching the disclosure rule does not automatically void the contract.
- Unhappiness with a deal is not the same as a legal ground, and a separation agreement cannot easily be changed later.
You signed a separation agreement, and now you think it was a mistake. Perhaps you later found assets you did not know about, felt you had no real choice, or never understood what you were giving up. You want to know if you can undo it.
It is sometimes possible, but courts do not undo agreements just because one side wishes they had bargained harder. This article explains the grounds, how a court approaches the question and what to do first. It is general information, and a lawyer can assess your facts.
Why it is hard to walk away
Ontario says you cannot easily change a separation agreement later. To be enforceable, a separation agreement must be in writing, signed by the parties and witnessed. The Court of Appeal for Ontario has held that an unwitnessed but signed separation agreement was enforceable on its facts, so a missing witness does not always end the matter.
The grounds a court looks at
Under s. 56(4) of the Family Law Act, a court may set aside a domestic contract or a provision in it on application in these situations:
| Ground | In plain words |
|---|---|
| Failure to disclose | A party did not disclose significant assets, or significant debts or liabilities, that existed when the contract was made |
| Lack of understanding | A party did not understand the nature or consequences of the contract |
| Contract-law grounds | Otherwise in accordance with the law of contract, for example duress |
Ontario's guidance also notes that a court may refuse to enforce a separation agreement if a party did not fully disclose financial information. Whether a particular situation, such as an unfairly one-sided deal, fits a contract-law ground depends on the facts, and a lawyer can confirm.
How the court decides
Courts apply a two-stage approach. First, the person applying must prove that a listed ground applies. Second, the court decides in its discretion whether to set the contract aside, and fairness is a consideration.
This means proving a ground does not guarantee the result. The Court of Appeal has held that breaching s. 56(4) does not automatically void the contract. How this applies to a particular provision of your agreement depends on your situation, so it is worth confirming with a lawyer.
For non-disclosure, the missing asset or debt generally needs to be significant and to have existed when the contract was made. Evidence matters: financial statements, bank and account records, and what you were told before signing.
The court process
Ontario describes the steps in most family court cases as: the Mandatory Information Program, first appearance (at Family Court branches, except cases involving divorce, property or an arbitration award), case conference, settlement conference, then trial scheduling and trial management conferences. A case starts with Form 8 (General Application) where the parties disagree. In most circumstances both parties must attend a free Mandatory Information Program.
Financial disclosure is central. Financial statements are Form 13 where only support is claimed and Form 13.1 where property or debts are claimed, and both are commissioned. The other side responds with an Answer (Form 10) within 30 days, or 60 days if served outside Canada and the U.S.. Exactly how an application about an existing agreement fits into this process depends on your case, so confirm it with a lawyer.
If the agreement deals with support and you only want different terms going forward, that may be a different route. Where both agree, a consent motion to change (Form 15C) is filed, and if the other spouse disagrees, a motion to change (Form 15).
Why timing and conduct matter
Courts look at what happened when you signed. Did you have your own lawyer? Ontario's guidance says each party should get independent legal advice before signing, and the Law Society of Ontario says a lawyer giving that advice should give the client a written certificate. Time limits for this kind of application are not covered here, so get advice promptly.
Mediation is another option. It is voluntary and closed (confidential) unless both parties agree it is open, and a mediator does not replace a lawyer.
What to do next
- Do not ignore deadlines or payment terms in the agreement while you decide what to do.
- Collect your copy of the agreement, drafts, emails and texts from the time of signing.
- List what you now believe was missing, such as assets, debts or income, and how you found out.
- Gather the financial disclosure you received, and whatever you can find about what was left out.
- Write down who was present, what pressure you felt and whether you had a lawyer.
- Speak with a family lawyer soon, because delay can hurt.
Frequently asked questions
Can I set aside a separation agreement just because it is unfair?
Not on that alone. A court first requires a listed ground, such as non-disclosure of significant assets or debts, lack of understanding, or a contract-law ground like duress. Only then does it decide in its discretion whether to set the agreement aside, with fairness a consideration.
What if my spouse hid assets?
Failure to disclose significant assets, or significant debts or liabilities, existing when the contract was made is a ground under s. 56(4). A breach does not automatically void the contract, so the court still decides.
Can a court cancel only the part I dislike?
Section 56(4) contemplates setting aside a contract or provision in its entirety. How that applies to your agreement is something a lawyer can assess.
Does it matter that nobody witnessed my signature?
A domestic contract must be in writing, signed and witnessed to be enforceable. But the Court of Appeal has held an unwitnessed but signed separation agreement enforceable on its facts, so it depends.
Sources
- Superior Court of Justice – The Steps in a Family Case — ontariocourts.ca
- Ontario – Guide to Procedures in Family Court: Steps to filing an application — ontario.ca
- Superior Court of Justice – Guide to Process for Family Cases — ontariocourts.ca
- Ontario – Dividing property when a marriage or common law relationship ends — ontario.ca
- Ontario – Family mediation — ontario.ca
- Law Society of Ontario – Independent legal advice and independent legal representation — lso.ca
- Court of Appeal for Ontario – Climans v. Latner, 2020 ONCA 554 — ontariocourts.ca
- Court of Appeal for Ontario – Moses Estate v. Metzer, 2017 ONCA 767 — ontariocourts.ca
Links go to official government, court and regulator pages. The law changes — confirm you are reading the current version.
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