Notice of objection deadline: 90 days, or a year past the T1 due date

Objection deadlines by taxpayer type

Subsection 165(1) sets two clocks. An individual (other than a trust) or a graduated rate estate gets the later of one year after the filing due date for the year and 90 days after the notice was sent. Every other taxpayer gets the 90 days only laws-lois.justice.gc.ca.

The individual rule has carve outs. A loss determination, or tax assessed on an RRSP or TFSA overcontribution, gets 90 days from the notice even for an individual canada.ca. Corporations get 90 days from the date of the notice of assessment or reassessment, with no one year alternative canada.ca.

GST/HST works like a corporation: a written objection within 90 days after the day the notice of assessment is sent laws-lois.justice.gc.ca. The CRA counts from the date on the notice, not the day it reached your client canada.ca.

Worked example: four notices dated October 1, 2026

Count the 90 days from the day after the notice date. From October 1, 2026, that's 30 days left in October, 30 in November and 30 in December, so day 90 lands on December 30, 2026. For individuals, compare that to one year after the filing due date. The 2025 T1 was due April 30, 2026, or June 15, 2026 when your client or their spouse is a sole proprietor canada.ca.

The one year window covers reassessments too, because "assessment" includes a reassessment in subsection 248(1) laws-lois.justice.gc.ca. That's why the 2025 reassessment can wait until spring 2027, while the 2023 one can't. If the corporation misses December 30, 2026, its last day to apply for an extension is December 30, 2027.

Missed it: the one year extension under section 166.1

Your client can apply to the Minister for more time under subsection 166.1(1). The application gives the reasons the objection was late and goes to the Chief of Appeals with a copy of the objection attached laws-lois.justice.gc.ca.

Paragraph 166.1(7)(a) is the hard stop: the application must be made within one year after the objection deadline expired. Inside that year your client must also show three things laws-lois.justice.gc.ca:

If the CRA refuses, or 90 days pass with no decision, your client can apply to the Tax Court under subsection 166.2(1). That application must be filed within 90 days after the refusal was mailed, and the court applies the same one year limit and the same three tests laws-lois.justice.gc.ca.

GST/HST has its own extension in section 303, with the same one year limit in paragraph 303(7)(a) laws-lois.justice.gc.ca. The CRA's GST/HST page says to apply in writing to the Chief of Appeals at your Appeals Intake Centre and explain why the objection was late canada.ca.

How to file: My Business Account, My Account or Form T400A

Online is the fastest route. In My Account or My Business Account, select "Register my formal dispute" and you get a case number to quote on every document you send later. As an authorized representative you file the same way through Represent a Client canada.ca.

On paper, complete Form T400A, Notice of Objection (Income Tax Act) canada.ca. Mail or fax it to the Chief of Appeals at your Appeals Intake Centre canada.ca. A signed letter setting out the facts and reasons also counts as an objection canada.ca. For GST/HST the paper form is GST159, Notice of Objection (GST/HST) canada.ca.

Large corporations get stricter rules. The objection must reasonably describe each issue, state the relief sought for each issue as a change in an amount, and give the facts and reasons for each one laws-lois.justice.gc.ca. A large corporation, one with more than $10 million of taxable capital employed in Canada together with its related corporations, also pays 50% of the disputed amount while it objects canada.ca.

What happens after the objection is filed

For income tax, the CRA normally holds off collecting the amounts in dispute until 90 days after it sends its decision. Amounts your client had to withhold and remit are excluded canada.ca.

GST/HST is different. The Minister may collect the full amount owing even though an objection or appeal is filed, unless your client posts acceptable security canada.ca. Budget for the payment before you file.

The next deadline is the Tax Court. For income tax, the court must receive the notice of appeal within 90 days of the date the CRA sends its decision, and your client can appeal early if the CRA hasn't decided within 90 days of the objection canada.ca. For GST/HST, that early appeal opens only after 180 days without a decision canada.ca.