Can a Marriage Contract Waive Your Rights Under a Spouse's Will in Ontario?

Marriage contracts usually come up in conversations about what happens if a marriage ends in separation. They can also address something people think about less often: what happens if a marriage ends by death instead. A marriage contract can include clauses in which each spouse gives up certain claims they would otherwise be entitled to make against the other's estate, in exchange for what the contract — or the will itself — actually provides.

This matters most for blended families, couples where one spouse owns a business, and marriages with a significant gap in assets between spouses. Without a clear waiver, a surviving spouse can end up with a legal claim that competes with, or even overrides, what a will says. Whether that waiver survives being challenged later depends heavily on how — and when — it was signed.

Here is how these clauses generally work under Ontario law, and where their limits sit.

Two Different Claims a Surviving Spouse Can Have

Ontario's Family Law Act gives married spouses a right to equalization of net family property — broadly, sharing the growth in each spouse's net worth during the marriage. That right does not only apply when spouses separate. It can also apply when a marriage ends because a spouse dies.

In that situation, Ontario law generally gives the surviving spouse a choice: accept what the deceased spouse's will provides (or what they would receive on an intestacy, if there is no will), or make an equalization claim against the estate instead. A surviving spouse would typically choose whichever route leaves them better off.

A marriage contract's estate-waiver clause is aimed at that equalization-based claim specifically. It has each spouse agree, in advance, to give up the right to make it — leaving the will, or a specific arrangement set out in the contract, to control what each spouse actually receives.

How the Waiver Is Usually Built Into the Contract

A typical clause has each spouse acknowledge the estate claim they would otherwise be entitled to make, and expressly release it in favour of what the contract, the other spouse's will, or a named alternative (such as a life insurance policy or a trust) provides instead. Couples often pair this kind of clause with related terms addressing whether support obligations continue after death, since the two issues frequently arise from the same conversation.

Because this kind of clause is asking someone to give up a right that could otherwise be worth a great deal, courts scrutinize it more closely than an ordinary contract term — which is why the process behind the signing matters as much as the wording itself.

What Makes the Waiver Hold Up Later

Ontario's Family Law Act sets out formal requirements for any domestic contract, including a marriage contract: it must be in writing, signed by both spouses, and witnessed. No court approval is required at the time of signing.

Meeting those formalities is only the starting point. A waiver of estate rights is far more likely to be upheld years later — after one spouse has died and can no longer explain their side — if these were also true at the time:

• [ ] Each spouse made full and honest financial disclosure before signing
• [ ] Each spouse had independent legal advice from their own lawyer, not a shared one
• [ ] Both spouses genuinely understood what they were giving up, not just that a document existed
• [ ] The contract was signed without pressure and with real time to consider it
• [ ] The contract has been reviewed and, if needed, updated as circumstances changed

A court asked to enforce — or set aside — this kind of clause will look closely at whether the process was fair, not just whether the signatures and a witness are on the page.

What a Waiver Doesn't Touch

A marriage contract cannot be used to eliminate a spouse's obligation to support a child, and it generally cannot override what is in a child's best interests. It also does not automatically resolve every estate-related question. Rights connected specifically to the matrimonial home are treated differently under Ontario law, and a general estate waiver clause may not be enough to address them — that usually needs its own, separately considered clause.

It is also worth remembering that a marriage contract and a will are two different documents that need to work together. A waiver clause changes what claims a surviving spouse can make; it does not replace the will itself, which still needs to say where everything actually goes.

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