HIGH NET WORTH

Ontario law splits what grew during the marriage. A contract can change that — with one fixed exception.

Roughly a third of Ontario marriage contracts exist specifically to protect a business built before the wedding. Here's what they can actually do, what they legally can't, and what makes one hold up later.

This is an uncomfortable topic to plan for while things are good, which is exactly why so few people do it before they need to. For anyone bringing a business, a substantial inheritance, or significant pre-existing assets into a marriage, it's worth understanding clearly rather than avoiding entirely.

What Ontario's default rule actually does

Without a marriage contract, Ontario's Family Law Act doesn't simply split everything 50/50. It equalizes the growth in each spouse's net worth from the date of marriage to the date of separation. If your net worth grew more than your spouse's during the marriage, you pay them half the difference as an "equalization payment" — property brought into the marriage isn't automatically shared, but how much it grew during the marriage generally is.

What a marriage contract can change

A properly drafted contract (governed by section 52 of the Family Law Act) can modify or eliminate the equalization formula entirely for specific assets — commonly used to:

Exclude a business owned before the marriage from the equalization calculation
Protect an inheritance, including one received during the marriage
Define how debts each spouse brought in will be treated
Set expectations around spousal support, within real legal limits

Real Ontario data: roughly 35% of marriage contracts focus primarily on protecting pre-marital business assets, and about 25% on protecting inherited property — the two most common real-world reasons people use one.

The one thing that can't be contracted away. The matrimonial home is a fixed exception. Regardless of who owned it before the marriage, when it was purchased, or how the marriage contract is worded, both spouses generally retain equal rights to possession of the home used as the family residence — a marriage contract cannot remove this protection.

The trap that undoes protection without anyone noticing: commingling

How separate property quietly becomes shared

Bring $100,000 into the marriage and keep it in its own account, untouched — it generally stays your separate property. Use that same $100,000 to pay down the mortgage on the family home, or as collateral for a joint loan, and it can become part of the marital property subject to equalization — even with a marriage contract in place, if the contract wasn't specifically drafted to anticipate this. Keeping pre-marital and inherited assets genuinely separate, not just on paper but in practice, matters as much as the contract itself.

What actually makes one enforceable

Courts can — and do — decline to enforce a marriage contract that was signed under pressure or without real understanding of what was being given up. The Supreme Court of Canada's decision in Rick v. Brandsema made clear that enforceability depends on the integrity of the process, not just the paper itself.

Full, honest financial disclosure from both parties — hiding assets to get a more favourable contract can unravel the entire agreement later
Independent legal counsel for each spouse — separately, not the same lawyer for both, and not a shared "certificate of advice" signed in the hallway before the ceremony
Real time to review it — signing weeks (ideally months) before the wedding, not the night before, when duress becomes a far easier argument to make later
A genuinely fair outcome — courts weigh the overall fairness of the agreement, not just whether the paperwork was technically correct

Typical cost for a properly drafted Ontario marriage contract runs $1,500 to $10,000 with a lawyer on each side; online template services start around $429 but carry more real risk of being challenged later if the process wasn't handled carefully.

Where this connects to a family business

If a shareholder agreement already exists for a family business, it often contains its own valuation and buyout provisions that interact directly with a divorce — the two documents should be drafted together, not independently, so they don't quietly contradict each other.

Also worth knowing: common-law couples who never marry aren't automatically protected by any of this — the equivalent document is a cohabitation agreement, and the same principles apply. Family law is provincial in Canada, so the specific rules here reflect Ontario; other provinces have their own frameworks with real differences worth confirming locally.

See your real numbers, together or separately — a clear-eyed starting point for a conversation worth having early, not late.

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