CRA objection deadline calculator
The last day to dispute a notice of assessment or reassessment for your income tax return, and how much time you have left.
The short version
- Enter the date on your notice of assessment or reassessment and the tax year, and the calculator shows your last day to object and how many days are left.
- For individuals, it's the later of one year after the filing due date for that return, or 90 days after the date on the notice.
- Example: a notice dated May 12, 2026 for the 2025 return can be objected to until April 30, 2027. A reassessment of 2023 dated September 14, 2026: until December 13, 2026.
- Missed it? You can ask for an extension, but only within one year after the deadline.
- GST/HST notices are stricter: 90 days, with no one-year alternative.
CRA Objection Deadline Calculator
When CRA changes your return and you disagree, the deadline is the one date that matters more than the argument. Miss it and the best case for the CRA's mistake is a long, uncertain request for relief. Catch it and you have a formal right to have the decision reviewed by someone who wasn't involved. The calculator finds the date; the rest of this page covers what to do with it.
The Rule for Individuals
You can object until the later of two dates: one year after the filing due date for the return (April 30, or June 15 if you or your spouse had self-employment income), or 90 days after the date on the notice. For a recent reassessment of an old year, the 90-day date usually wins. For your normal assessment in spring, the one-year date usually wins. More on objection deadline rules.
Ready to object, but not sure what to say?
The CRA Objection SmartFile reads your notice, works out what changed and the deadline, and drafts the objection with the facts and documents CRA needs.
How to Object
Online through My Account (Register my formal dispute) or on form T400A by mail. Say what you disagree with, why, and include or offer the documents. You can send more documents later. You don't need a lawyer to file an objection. The full guide is on filing a notice of objection; what the notice says, on notice of reassessment. Not sure what changed? Run it through the notice analyzer.
Missed It?
You can ask CRA for an extension of time, but only within one year after the deadline, and you have to explain why you couldn't file on time. While an income tax objection is open, CRA generally won't collect the disputed amount, but interest keeps running. Paying and objecting stops the interest; you get it back with interest if you win. Penalties and interest: taxpayer relief.
Objection Deadline Questions
How long do I have to object to a CRA reassessment?
For individuals, the later of one year after the filing due date for that tax year, or 90 days after the date on the notice of assessment or reassessment.
What happens if I miss the objection deadline?
You can apply to CRA for an extension of time within one year after the deadline, explaining why you could not object on time. After that, the right to object is generally lost.
Is the deadline different for GST/HST?
Yes. GST/HST objections must be filed within 90 days of the notice, with no one-year alternative.
Do I have to pay while my objection is open?
For income tax, CRA generally does not collect the disputed amount while an objection is open, but interest keeps running. Paying stops the interest and you get it back with interest if you win.
How do I file an objection?
Online through My Account using Register my formal dispute, or on form T400A by mail. Explain what you disagree with and why, with your documents.
Sources: CRA, P148, Resolving your dispute. Checked October 2026. Estimates only, based on the rules as last checked. CanadianTaxes.ai is not the Canada Revenue Agency and does not give tax advice.
Last reviewed October 5, 2026 against CRA and Government of Canada sources. How we check our facts.
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