When Does the CRA Consider You Common-Law? The Tax Definition Explained

Many Ontario couples assume that "common-law" means the same thing to the CRA as it does under provincial family law. It doesn’t always. The CRA applies its own test for when two people become common-law partners for tax purposes, and that test can be triggered earlier, later, or differently than what a family law lawyer would tell you about property or support rights.

Understanding the CRA common-law definition matters because it determines when you’re required to start reporting your relationship on your tax return — and getting it wrong in either direction can create real problems down the line.

The CRA’s Two-Part Test

For tax purposes, the CRA generally treats you as common-law once either of the following applies:

1. A duration test: you’ve been living together with your partner in a conjugal (marriage-like) relationship for a continuous period the CRA treats as sufficient to establish common-law status.
2. A child-based test: regardless of how long you’ve lived together, you’re considered common-law once you have a child together by birth or adoption, or one of you supports the other’s child.

The child-based test is the one people most often miss. Couples sometimes assume common-law status only starts "after a while," not realizing that having a child together can trigger it right away, independent of how long the relationship has lasted.

How This Can Differ from Ontario Family Law

Ontario family law and the Income Tax Act ask different questions for different reasons. Family law is generally concerned with property division, support obligations, and rights on separation, and Ontario’s own tests for when a relationship qualifies for a particular family law purpose don’t map exactly onto the CRA’s test. It’s entirely possible to be common-law for tax purposes at a different point than you’d be considered a "spouse" for a particular Ontario family law claim, or vice versa. Don’t assume that a family law lawyer’s answer about your relationship status also settles your CRA reporting question, or the reverse — each is measured against its own test.

When You Must Tell the CRA

Once you meet the CRA’s test, you’re expected to report your status as common-law on your next tax filing and to update your marital status with the CRA going forward, generally at the point your situation changes rather than waiting for tax season. Your benefits — including the GST/HST credit and the Canada Child Benefit, if you have children — are then calculated on your combined family income rather than your individual income alone.

What Happens If You Get It Wrong

• Reporting too late: if you meet the CRA’s test but keep filing as single, your benefit calculations are based on incomplete information. The CRA can reassess once it identifies the discrepancy, which can mean repaying benefits you weren’t entitled to as a single filer.
• Reporting too early: claiming common-law status before you actually meet the test can also misstate your benefits and credits, in either direction.
• Assuming a shared lease or joint account settles it: living at the same address or sharing finances is evidence relevant to the test, but it isn’t automatically determinative on its own — the CRA looks at the whole relationship.

Signs You May Already Meet the Test

• [ ] You and your partner have lived together continuously in a relationship for a lengthy stretch
• [ ] You have a child together, whether by birth or adoption
• [ ] One of you financially supports the other’s child
• [ ] You present yourselves publicly as a couple and share significant financial responsibilities

None of these signs is decisive on its own. The CRA looks at the whole picture, and if your situation feels close to the line, it’s worth getting a clear answer rather than guessing and hoping it doesn’t come up later.

Frequently asked questions