Using a Marriage Contract to Protect a Family Business or Inheritance in Ontario

If you're a business owner, a professional with a practice, or someone who expects to inherit family assets — and you're getting married — a marriage contract may be one of the most important business and estate planning decisions you'll make.

Ontario's equalization rules mean that if your marriage ends, your spouse may be entitled to half the increase in your net family property accumulated during the marriage. Without a marriage contract, the value growth of a family business, a professional practice, or an asset you inherited could be subject to equalization — even if your spouse had nothing to do with building it.

This article explains how Ontario marriage contracts can protect those assets, and what careful drafting requires.

How Ontario Equalization Works (Briefly)

When a marriage ends in Ontario, the Family Law Act calculates each spouse's net family property — essentially the net assets each person accumulated from the date of marriage to the date of separation. The spouse with the higher net family property pays the other spouse half the difference. This is called an equalization payment.

By default, almost everything accumulated during the marriage counts — including the increase in value of a business you owned before or started during the marriage.

Important exception: Assets received as gifts or inheritances during the marriage (not before) are excluded from the calculation — but only if they haven't been commingled with marital assets in a way that makes the exclusion impossible to trace. And the increase in value of pre-marital property is included in the equalization calculation.

This is where marriage contracts become essential for business owners and people with family wealth.

What a Marriage Contract Can Do

1. Exclude Pre-Marital Business Value and Its Growth

By default, the value of a business you owned before marriage is already your excluded property (its value at the date of marriage is deducted from your net family property calculation). But growth in that business's value during the marriage is included — and that's where the exposure lies.

A marriage contract can extend the exclusion to cover the growth in the business's value during the marriage. This doesn't mean the other spouse gets nothing — it means they don't receive a claim against a business you built, often with years of effort before and during the marriage, that your spouse had no operational role in.

2. Define How the Business Is Valued

Business valuation is one of the most expensive and contested aspects of family law litigation. A marriage contract can specify:

• How the business will be valued (e.g., the most recent independent valuation, or a formula)
• Who conducts the valuation and on what timeline
• Whether goodwill is included or excluded in the calculation

Defining the methodology in advance eliminates a major source of conflict and cost.

3. Protect Inherited Assets

Ontario law excludes gifts and inheritances received during the marriage from equalization — but this protection has limits:

• If you invest the inheritance in a joint asset (like the matrimonial home), it may lose its excluded status
• The matrimonial home itself loses the benefit of a pre-marital or inherited value deduction

A marriage contract can:

• Extend exclusion to inherited assets that would otherwise become subject to equalization
• Define what happens if inheritance money is contributed to jointly-held property
• Address the matrimonial home specifically to preserve pre-marital or inherited equity

4. Address the Matrimonial Home

Under Ontario's default rules, the matrimonial home receives no deduction for value brought into the marriage. If you owned your home before the wedding, the full value at separation — not just the appreciation — is included in your net family property. A marriage contract can restore the deduction for pre-marital equity.

5. Limit Spousal Support Exposure

For business owners, spousal support is a particular concern because self-employment income can fluctuate and courts sometimes impute income in complex ways. A marriage contract can agree on support terms in advance, limiting uncertainty.

What the Contract Cannot Do

Even a well-drafted marriage contract has limits:

• Child support cannot be waived or limited — it belongs to the children
• Decision-making responsibility and parenting time are not controlled by a marriage contract
• Unconscionable provisions will be struck — a contract that leaves one spouse with nothing after a long marriage where they sacrificed career for family is likely to be challenged

The goal is protection of legitimate pre-marital and inherited assets — not stripping a long-term spouse of any economic security.

Why Business Owners Need More Than a Standard Template

Protecting a business in a marriage contract requires:

1. A clear picture of the business's current value — often requiring an independent business valuator
2. Careful description of what is being excluded — vague language like "the business stays mine" is not adequate
3. Provisions for value growth — distinguishing between growth attributable to general market conditions vs. marital effort
4. Consideration of corporate structures — shares, holding companies, operating entities, and shareholder agreements all interact with family law
5. Coordination with estate and corporate planning — the marriage contract should complement, not contradict, your will and shareholder agreement

This is specialized work. A generic domestic contract template will not do it.

The Process for Business Owners

1. Engage a family law lawyer early — ideally three to six months before the wedding
2. Get a business valuation as at the date of marriage (or as current as possible if the contract is signed during the marriage)
3. Exchange complete financial disclosure, including the valuation, business financial statements, and personal net worth
4. Negotiate and draft the agreement with each party's independent lawyer
5. Both parties receive independent legal advice and the lawyers sign ILA certificates
6. Sign and store the agreement along with the supporting financial disclosure

Frequently asked questions