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№ 77 Family Law

What Does Significantly Unfair Mean for a BC Marriage Agreement?

Learn how the significantly unfair test in the BC Family Law Act works for property and spousal support agreements, and which factors a court considers.

Family Law5 min readTSLBy the Treadstone Law Team · British ColumbiaUpdated November 6, 2026
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Key takeaways
  • Even when no one was misled or pressured, the Supreme Court may set aside or replace a property agreement or spousal support agreement that is significantly unfair.
  • The factors are not the same for every agreement: property agreements have three, and spousal support agreements have five.
  • Where one of the listed grounds is proven, the court may still decline to act if it would not replace the agreement with an order substantially different from its terms.

You signed a marriage agreement, prenup or separation-type agreement, and now one of you thinks it no longer works. Maybe you want out of it. Maybe you are the one trying to hold your spouse to it. Either way, you have probably seen the phrase "significantly unfair" and wondered what it actually requires.

This article explains where that test sits in the British Columbia Family Law Act, which factors the Act lists, and how it differs from the more familiar grounds such as hidden assets. It is general information only. Whether a particular agreement would survive depends on the facts, so a lawyer should look at your documents.

This article covers the law of British Columbia.

Two doors to challenging an agreement

The Family Law Act gives the Supreme Court two different routes for reviewing a written property agreement that each spouse signed in front of a witness. The first route is a list of specific circumstances. The court may set aside or replace all or part of the agreement on a spouse's application only if one of those circumstances existed when the agreement was made.

The second route is the significantly unfair test. Even where none of those circumstances existed when the agreement was made, the Supreme Court may set aside or replace all or part of a property agreement if it is significantly unfair. This is the door people use when nothing improper happened at signing but the result, viewed later, is hard to defend.

The factors for a property agreement

For property agreements, the Act names three factors the court considers when it decides whether an agreement is significantly unfair.

In plain words, the Act points the court toward finality. A long-standing agreement that both people planned their lives around, and that was meant to settle things for good, is harder to undo than a recent one that nobody has acted on. The listed factors do not include a change in either spouse's circumstances; that factor appears only in the spousal support version of the test.

The factors for a spousal support agreement

Spousal support agreements have their own set-aside rules. If no listed circumstance existed at signing, the court may still set aside or replace all or part of a spousal support agreement, including a waiver, if it is significantly unfair. It considers five factors: the time that has passed, changes since the agreement in a spouse's condition, means, needs or other circumstances, the spouses' intention to achieve certainty, their reliance on its terms, and the degree to which the agreement meets the objectives of spousal support.

Those objectives are to recognize economic advantages or disadvantages to the spouses, apportion the financial consequences of child care, relieve economic hardship from the breakdown, and, as far as practicable, promote each spouse's economic self-sufficiency within a reasonable period.

FactorProperty agreementSpousal support agreement
Time since the agreementYesYes
Intention to achieve certaintyYesYes
Reliance on its termsYesYes
Changes in a spouse's condition, means or needsNot listedYes
Meeting the spousal support objectivesNot listedYes

Limits on what the court will do

Proving a problem does not automatically end an agreement. For property agreements, the court may decline to act, even where a listed circumstance is proven, if on all the evidence it would not replace the agreement with an order substantially different from the agreement's terms. Spousal support agreements have a similar safeguard.

Witnessing also matters. The set-aside regime applies to a written agreement with each spouse's signature witnessed by at least one other person, and the same person may witness both signatures. An unwitnessed signed agreement is not automatically void, because the court may apply the same rules to it if that is appropriate in all the circumstances, but it is not clearly within the protected regime. The same idea applies to spousal support agreements.

What to do next

Whether you want to challenge an agreement or defend one, start by pulling together the facts a court would look at. A lawyer can then tell you how the factors may apply to your situation.

Frequently asked questions

Does the court have to set aside a significantly unfair agreement?

No. The Act says the Supreme Court may set aside or replace all or part of such an agreement, which leaves it with discretion. Separately, where one of the listed circumstances such as non-disclosure is proven, the court can decline to act if it would not replace the agreement with an order substantially different from its terms.

Is a lawyer required for the agreement to be valid?

The sections of the Act on property and spousal support agreements do not make a lawyer or independent legal advice a condition of validity. The Province's guidance does advise getting legal advice before making final decisions about property and debt.

Can I use this test if we were never married?

Possibly. The same rules apply to spouses whether married or not. Unmarried partners are spouses if they have lived together in a marriage-like relationship for a continuous period of at least 2 years, or, except in Parts 5 and 6 of the Act, if they have a child together. Whether you qualify depends on your facts.

Does the test apply to child support or parenting terms?

Those are handled differently. An agreement about parenting arrangements is binding only if made after separation or when the parties are about to separate, and on a party's application the court must set aside or replace terms that are not in the child's best interests. Child support agreements have their own rules.

Sources

Links go to official government, court and regulator pages. The law changes — confirm you are reading the current version.

This article is general information, not legal advice. Reading it does not create a lawyer-client relationship. British Columbia laws, tax rates, and government programs change, and how the law applies depends on your specific facts. For advice about your situation, speak with a lawyer who practises in British Columbia. Reach us at 1-844-900-1070 or send our Team a message.

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