Most tax disputes with the Canada Revenue Agency are lost on a calendar, not on the facts. The rules governing T400A are short, strict and unforgiving once a date slips past. Filing is how you formally dispute what the Agency has assessed. An objection is the first step in the dispute process, and it is the step most people get wrong on timing. This guide walks through the form itself, the deadline arithmetic, what a persuasive filing contains, and the two routes back in when you are already late.
Key Takeaways
- Filing an objection with the CRA moves your file out of the auditor’s hands and into its Appeals branch.
- The clock starts on the date printed on your notice, not the date you read it.
- Corporations and most trusts get 90 days to file a notice of objection. Individuals usually get longer.
- Late filers have one extra year, and that outer limit cannot be extended by anyone.
- File your objection on time and every argument stays open. Miss the date and the merits stop mattering.
- Interest keeps accruing on the disputed balance the entire time.
What Form T400A Does and When You Need It
T400A is CRA’s Notice of Objection form under the Income Tax Act (ITA). Complete Form T400A and you convert a disagreement into an income tax objection with legal consequences. When you file an income tax objection, your file leaves the auditor who assessed you and moves to an appeals officer in a separate branch, who reviews it fresh rather than defending the original decision.
You can object to a notice of assessment or notice of determination, and to a notice of reassessment or redetermination. What you cannot do is dispute an assessment that has not been made, so a proposal letter is out of reach. At that stage you are still in the audit, and written submissions to the auditor are the right tool. Our guide to your notice of assessment explains which document you actually hold.
Two limits are worth stating plainly. You file an objection to a notice, not to an auditor’s opinion, and you object to the assessment of your income tax return rather than to the return itself. An objection allows you to put facts in front of a reviewer that the auditor never saw. The Taxpayer Bill of Rights includes a right to a formal review of a decision, and this is how you use it. If you want to dispute a notice of assessment for payroll source deductions, the same route applies.
The form is not compulsory. A signed letter containing the same information can be used to file an objection, and ITA 165(6) lets the Minister accept one that was not served in the manner the Act requires. What is compulsory is the timing.
The Notice of Objection Deadline: 90 Days or One Year
The time limit for filing an objection depends on who you are:
| Who you are | Deadline to object |
|---|---|
| Individual or graduated rate estate | The later of one year after your filing due date for that year, or 90 days after the notice was sent |
| Corporation | 90 days after the notice was sent |
| Most trusts | 90 days after the notice was sent |
Both limits appear in ITA 165(1), and the wording matters. The period runs from the day of sending, so the date of the notice governs and the day you receive your notice is irrelevant. Mail delays, a change of address and an unread email notification in My Account all fail as excuses. Once you have received a notice you disagree with, the clock is already running.
Worked example. CRA reassesses Dev’s 2023 personal tax return on 4 March 2026. His 2023 filing due date was 30 April 2024, so one year after it landed on 30 April 2025, already gone. His deadline therefore becomes 90 days after 4 March 2026, which is 2 June 2026. Had CRA reassessed him in October 2024 instead, he would have had until 30 April 2025, roughly six months.
Corporations get no such cushion. A company must file a notice of objection within 90 days of the sending date and nothing more, which is why year-end reassessments often surface during a shutdown period and expire unnoticed.
How to File an Objection: Online, by Mail or by Letter
Three channels work when you want to file an objection, and they are not equally reliable:
- Online, through your CRA account: My Account, My Business Account or Represent a Client, using the service for registering a formal dispute. Filing an objection online is the fastest route and it gives you a case number instantly.
- By mail. Filing an objection by mail means sending T400A or your letter to the Chief of Appeals at the Appeals Intake Centre, whose Sudbury, Ontario address is listed in the Agency’s guide P148. Use tracked delivery, because the postmark is your evidence.
- By fax, to the eastern or western Appeals fax number listed in the same guide. Keep the transmission report.
The current version of the form sits on the forms pages at canada.ca, and you should download T400A rather than reuse an old copy. Whichever channel you pick, and whatever the type of objection, save dated proof the same day. When a filing date is later questioned, the business that kept a tracking number wins that argument in one email. Do not contact the CRA by phone and assume the call counted, because only a filed objection stops the clock.
What to Include When You Dispute a CRA Assessment or Reassessment
An appeals officer opens your file with the auditor’s working papers already in front of them. Your job is to give them a cleaner version of events, organised the way they must decide it. Include:
- Every tax year in dispute, listed separately with the date on the notice of assessment or determination.
- The specific adjustments you disagree with, by line or by schedule.
- The dollar relief you want on each one, stated as a number.
- The facts you rely on, in date order, with documents attached.
- The reasons for your objection, set out issue by issue.
- The legal basis, even briefly: the ITA provision, folio or case that supports you.
Whether you file a formal objection on T400A or by letter, the content matters far more than the container. You also need to include personal information that identifies you, such as your social insurance number or business number, along with the years involved and the amount in dispute. The officer reads the reasons for the objection before anything else, so put them near the front rather than in a closing paragraph.
In our CRA representation practice, the objections that resolve in a single exchange share one feature: they hand the officer a reconciling schedule that ties your figures to the auditor’s, adjustment by adjustment. Objections written as a narrative of how unfair the audit felt take three exchanges longer and rarely land better. Where penalties are also in play, address them separately, because gross negligence penalties turn on the taxpayer’s state of mind rather than on the underlying numbers.
Large Corporations Face Stricter Objection Rules
A large corporation, meaning one whose taxable capital employed in Canada exceeds $10 million under ITA 225.1(8), files under a tighter standard. Under ITA 165(1.11) its notice of objection must reasonably describe each issue, specify the relief sought as an amount, and provide the facts and reasons for each issue. If the relief or the facts and reasons for an issue are missing, ITA 165(1.12) lets the Minister ask for them in writing, and supplying them within 60 days cures the gap.
Miss that and the consequence is permanent. Under ITA 169(2.1) the corporation can appeal to the Tax Court only on the issues it described and for the relief it specified, so a point left out cannot be added later. Collection is harsher too: ITA 225.1(7) lets CRA pursue half the disputed amount while the dispute is live.
Missed the Deadline to File a Notice? Two Extension Routes
Being late is survivable for exactly one year. ITA 166.1 lets you apply to the Minister to extend the time, provided the application is made within one year after the objection filing deadline expired. You must also show that you were unable to act or genuinely intended to object within the period, that granting the request is just and equitable, and that you applied as soon as circumstances allowed.
Under ITA 166.1 the application must also be accompanied by a copy of the objection itself, so the original objection and the request travel together. Draft both at once rather than filing the request and promising the rest later.
CRA is generally the first decision-maker here. If it refuses, or simply does not answer within 90 days, ITA 166.2 lets you take the same application to the Tax Court.
What no one can extend is the one-year outer limit. In Oliveira v. The King, 2023 TCC 33, a British Columbia teacher was assessed as a director and objected on time, but missed the 90-day window to appeal after CRA confirmed the assessments in May 2021. His originals were destroyed and CRA issued replacements that August, still inside the grace period. He applied for more time in September 2022, under ITA 167, which sets the same one-year outer limit for late appeals that ITA 166.1 sets for late objections. Justice Spiro dismissed both applications because the year had run, without reaching whether he had ever been a director at all.
That is the practical lesson. The outer limit is jurisdictional, so the strength of your position becomes irrelevant the moment it passes.
What Happens After a CRA Notice of Objection Is Filed
The objection process runs through the Appeals Branch, where an officer reviews the file, may contact you with a CRA information request for missing details, and decides: CRA will send a reassessment if it agrees with you in whole or in part, or a notice confirming the assessment if it does not, with an explanation either way. You may not receive a reply for months, but once 90 days pass without one, ITA 169(1)(b) lets you file an appeal with the Tax Court of Canada. Our CRA appeals process guide covers that review, its outcomes and every court stage after it, and tax court appeal timelines show how long the court stage runs. Resolving your dispute at the objection stage is almost always cheaper than litigating it afterwards.
Collection pauses in the meantime, but only for income tax. ITA 225.1(2) stops CRA from collecting the amount in controversy until 90 days after it confirms or varies the assessment. Two carve-outs matter: source deductions and other withheld amounts stay collectible under ITA 225.1(6), and large corporations face the 50% rule above.
GST/HST works differently, and this catches owner-managers out. The Excise Tax Act contains no equivalent stay. Section 315 gives the Minister only a discretionary power to postpone collection on a disputed amount, so an HST assessment remains payable while you argue about it. Meanwhile interest continues to compound on any balance you ultimately owe, which is why paying under protest sometimes beats winning slowly.
Frequently Asked Questions
How long does a notice of objection take with CRA?
There is no statutory time limit, only the obligation to act with all due dispatch. The CRA reports that low-complexity income tax objections resolved in June 2026 took 127 days on average, and medium-complexity ones, such as business expense disputes, took 389 days. You can bypass the wait by appealing once 90 days have elapsed.
What is the deadline for filing a notice of objection?
For corporations and most trusts the deadline to file an objection is 90 days from the day the notice was sent. Individuals get the later of that 90 days or one year after their filing due date for the year. The 90-day window runs from the sending date, so an envelope opened late changes nothing.
Where can I find the CRA objection form?
T400A sits on CRA’s forms and publications pages, and the online service in My Account or My Business Account collects the same information without the paper. Download a current copy each time rather than reusing a saved file, because the form is revised periodically.
Do I have to use the T400A form to file an objection?
No. A signed letter containing the same information is valid, and ITA 165(6) permits the Minister to accept a filing that was not served in the manner the Act requires. The form is still worth using because it prompts you for everything a reviewer needs.
What happens if I file my objection late?
You apply for an extension under ITA 166.1 within one year of the missed deadline, explaining why you were late. Past that year, no extension is available from CRA or from any court. An individual can still ask for a refund or reduction for an older year under the taxpayer relief provisions, and anyone can ask for penalty and interest relief, but neither route is an objection.
Can CRA collect the tax while my objection is pending?
For income tax, generally no, until 90 days after CRA confirms or varies the assessment. Payroll withholdings are exempt from that protection, large corporations remain liable for half the disputed amount, and GST/HST assessments carry no automatic hold at all.
What happens if CRA confirms the assessment?
You have 90 days from the notice of confirmation to file a notice of appeal with the Tax Court of Canada. The choice between a further objection or appeal does not really arise, because a confirmed assessment moves to the court rather than back to the branch that confirmed it.
Can I object to penalties and interest?
Penalties can be disputed through an objection because they form part of the assessment. Interest follows the tax, so it falls if the tax is reduced. To have interest or a penalty cancelled because of circumstances beyond your control, you request taxpayer relief under ITA 220(3.1) instead, and you cannot object to that decision.
The Bottom Line
An objection is procedurally simple and substantively demanding. The form takes an hour, while the evidence behind it decides the outcome.
- Diarise the date of your notice immediately, then work backwards from the applicable deadline.
- State the relief you want as a dollar figure on each disputed adjustment.
- Attach the reconciling schedule, not a narrative of the audit.
- File your notice of objection before the date, not after the documents feel perfect.
- Treat the one-year extension window as a hard wall, because every court does.
Whether an objection is your best move depends on what the auditor actually assessed, how strong the documentation is, and what a reassessment would cost against the interest clock. Those variables differ on every file, so a review before filing is usually worth more than a faster submission. Our CRA representation team handles objections from intake through to appeals, and you can reach us here to talk through a notice you have already received.
