- Under the Income Tax Act, the CRA generally has a fixed window after issuing your original Notice of Assessment to reassess that year — the normal reassessment period.
- The normal reassessment period is a default, not an absolute wall.
- On an ordinary, timely reassessment, the taxpayer generally bears the burden of showing the CRA's number is wrong.
Most Ontario taxpayers assume that once enough time has passed, an old tax year is simply closed — the CRA can't touch it anymore. That's mostly true, and the concept has a name: a statute-barred year. But "mostly" is doing real work in that sentence, because the Income Tax Act gives the CRA specific exceptions to reopen a year that would otherwise be off-limits.
If you're being audited for a year you thought was long settled, understanding the normal reassessment period — and the narrow doors the CRA can use around it — tells you whether the CRA is on solid ground.
What "Statute-Barred" Means
Under the Income Tax Act, the CRA generally has a fixed window after issuing your original Notice of Assessment to reassess that year — the normal reassessment period. Once that period expires without the CRA reassessing, the year is statute-barred: the CRA can no longer reassess it under the ordinary rules, and you can generally treat the numbers as final.
The length of the normal reassessment period depends on the type of taxpayer:
| Taxpayer | Normal reassessment period |
|---|---|
| Individuals and Canadian-controlled private corporations (CCPCs) | 3 years from the date the original Notice of Assessment was sent |
| Other corporations and mutual fund trusts | 4 years from the date the original Notice of Assessment was sent |
The clock runs from the day the CRA sent your original assessment (or a notification that no tax was payable, if that came first) — not from your filing date, and not from the date you received the notice in the mail.
The Exceptions: How CRA Can Reopen a Statute-Barred Year
The normal reassessment period is a default, not an absolute wall. The CRA can reassess a statute-barred year where it can show one of the following:
- Misrepresentation attributable to neglect, carelessness, or wilful default. This covers everything from a genuinely careless omission to deliberate misstatement — the standard doesn't require intent to deceive, just a failure to take reasonable care in how the return was prepared.
- Fraud. Deliberate deception in the filing.
- A signed waiver. If you signed a waiver for that tax year (often at the CRA's request during an active audit), the normal reassessment period doesn't apply to whatever the waiver covers, for as long as it remains in effect.
Outside of these three routes, a truly statute-barred year stays closed, and the CRA carries the burden of establishing that one of the exceptions applies before it can reassess.
The Burden of Proof Matters Here
On an ordinary, timely reassessment, the taxpayer generally bears the burden of showing the CRA's number is wrong. But when the CRA wants to reopen a statute-barred year on the basis of misrepresentation, the CRA has to justify reopening it — it isn't enough for the CRA to simply disagree with how a return was filed years after the fact. This distinction is often the actual battleground in disputes over old tax years, separate from whatever the underlying tax issue is.
Why You Might Be Asked to Sign a Waiver
If you're under audit and the normal reassessment period for a year is about to expire, the CRA may ask you to sign a waiver extending its ability to reassess that specific year and issue beyond the normal deadline. This is a common request, not evidence of wrongdoing, and it protects the CRA's ability to complete the audit — but signing it also gives up ground you'd otherwise keep by simply letting the deadline pass. Get advice before signing, particularly on how narrowly the waiver is worded and what it does and doesn't extend.
Practical Signs You Might Be in Statute-Barred Territory
- The tax year under audit ended well beyond the applicable 3- or 4-year window from your original assessment
- You never signed a waiver for that year
- The CRA hasn't alleged fraud or made a specific claim of misrepresentation — it's simply revisiting the year
- You have no reason to believe the original return contained anything more than an honest position, even if arguable
None of these on their own settle the question — only a review of your specific assessment dates, filing history, and any waiver can confirm whether a year is genuinely closed.
Frequently asked questions
If the CRA reassesses a year I think is statute-barred, what should I do?
Don't assume the CRA is wrong just because the year feels old — but don't assume it's automatically entitled to reassess either. Get the specific dates (when your original assessment was sent, whether you signed any waiver) reviewed before responding, since this is often a legal question about burden of proof, not just arithmetic.
Does filing an amended return restart the reassessment clock?
Filing an amendment doesn't extend the normal reassessment period for the original assessment, though it can trigger its own review. This is a fact-specific question and worth confirming with a tax professional for your situation.
Can I refuse to sign a waiver if the CRA asks for one?
Yes — signing is voluntary. Declining doesn't stop an active audit, but it does mean the CRA's ability to reassess that year is limited by whatever time remains in the normal reassessment period.
Is a "careless" mistake really enough for CRA to reopen an old year, even without fraud?
Yes — misrepresentation attributable to neglect or carelessness is a lower bar than fraud, and it's one of the statutory grounds for reopening a statute-barred year. Whether a specific error meets that standard is exactly the kind of question worth getting legal advice on.
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