Common-Law Definition: CRA vs. Ontario Family Law Explained

"Are we common-law yet?" is a question a lot of couples in Ontario ask themselves at some point — usually right after moving in together, or right before filing a tax return. The frustrating answer is that it depends entirely on which law you're asking about, because the Canada Revenue Agency and Ontario's family law system use two different definitions that don't line up.

Understanding the gap between the CRA's common-law definition and Ontario family law's spouse definitions matters for two very different reasons: one determines how you file your taxes, and the other determines whether you have any claim to property or support if the relationship ends. Meeting one definition does not mean you automatically meet the other.

The CRA Definition: Built for Tax Filing

For federal tax purposes, the CRA treats two people as common-law partners once they've been living together in a conjugal relationship for a continuous period, or sooner in some circumstances such as sharing a child together. Once that threshold is met, you're generally required to identify as common-law on your tax return, whether or not you feel "married" in any legal sense.

This definition exists purely to determine tax filing status, benefit eligibility, and related administrative questions. It says nothing about:

• Whether you have a claim to your partner's property if you separate
• Whether you're entitled to spousal support
• Whether the home you live in gets any special legal protection

The CRA's rule is about when the government considers you a couple for tax and benefit purposes — full stop.

The Family Law Definition: Built for Property and Support

Ontario family law asks a different question entirely, and it splits into two separate tracks:

Property division — the FLA does not extend to common-law partners at all

Under the Family Law Act, the equalization of net family property — the sharing of growth in net worth built up during a relationship — applies only to married spouses. Common-law partners in Ontario get no automatic right to equalization, regardless of how long they lived together. This surprises a lot of people, because it means meeting the CRA's common-law threshold for tax purposes creates no parallel property right under family law. If you want property protection as a common-law couple, it has to come from a cohabitation agreement or from other legal doctrines (such as a trust claim) — not from the FLA's equalization scheme.

Spousal support — a separate, higher bar

An unmarried partner can qualify as a "spouse" for spousal support purposes under the Family Law Act, but only by meeting the Act's own test: continuous cohabitation for a minimum period set out in the Act, or being in a relationship of some permanence and parents of a child together. This is a distinct legal threshold from the CRA's tax definition — meeting one does not automatically mean you meet the other, and meeting the support definition still doesn't open the door to any property claim.

Side-by-Side: Why the Definitions Diverge

Why the Gap Trips People Up

The most consequential misconception in this area is the idea of a "common-law marriage" that grants property rights after living together long enough — Ontario has no such thing. You can be common-law for CRA purposes for years, file joint benefit applications, and still walk away from the relationship with no statutory claim to your former partner's property, no matter the length of cohabitation. Any property claim has to be built through a cohabitation agreement, or pursued through general trust or property law — both a different and generally harder path than the equalization scheme married spouses use.

The reverse gap matters too: someone might not think of themselves as "common-law" in the everyday sense, but if they've crossed the CRA's cohabitation threshold, they're required to file as such — independent of whatever their family law rights turn out to be.

What This Means Practically

• Filing your taxes correctly is a CRA question, answered by the CRA's own cohabitation rule — get this wrong and you risk a reassessment.
• Protecting property if you separate is a family law question, and for common-law couples, protection generally has to be built proactively through a cohabitation agreement, since the default statutory scheme won't provide it.
• Qualifying for spousal support sits in between — a real possibility for common-law partners, but only if the Family Law Act's own cohabitation or relationship test is independently met, not simply because the CRA already treats you as common-law.

Frequently asked questions