A notice of objection is the formal, statutory step a Canadian taxpayer takes to dispute a Canada Revenue Agency reassessment. If you have received a notice of reassessment, a notice of determination, a notice of confirmation, or a penalty assessment that you believe is wrong, the objection is how you challenge it — and, just as importantly, how you preserve your right to take the matter to the Tax Court of Canada later. This guide walks through the process from start to finish: the deadlines, the form, what to put in the document, the special rules for large corporations, and what to expect once the file lands on an Appeals officer's desk.

What a notice of objection actually is

A notice of objection is a written submission to the CRA stating that you disagree with a reassessment, identifying the issues in dispute, and setting out the facts and legal arguments that support your position. Filing it does two things at once.

First, it preserves your appeal rights. With very narrow exceptions, you cannot appeal a reassessment to the Tax Court of Canada unless you first filed a valid objection. Miss the objection deadline and you generally lose the right to litigate the issue at all. The objection is the gateway, not an optional first step.

Second, it moves your file to a fresh set of eyes. When you file an objection, the file is taken away from the auditor or determination officer who made the reassessment and transferred to the CRA Appeals Division. An Appeals officer is a different, more senior CRA employee whose job is to review the file independently. Appeals officers do reverse audit decisions, and they have authority to settle disputes on a principled basis. For many taxpayers, the Appeals stage is the most cost-effective opportunity to resolve a dispute without going to court.

The deadlines you cannot afford to miss

The objection deadline is statutory, which means the CRA has no discretion to simply ignore a late filing — you have to apply for relief, and relief is not automatic. The deadline depends on who you are and what kind of tax is involved.

Individuals and testamentary trusts (income tax)

For individuals, the deadline is the later of:

90 days from the date printed on the notice of reassessment, or
one year from the original return's filing-due date.

The "later of" rule often gives individuals more time than they expect. If you were reassessed for the 2024 tax year shortly after filing, the one-year-from-filing-due-date branch may extend your window well past the bare 90 days. But you should never count on it — calculate both dates and treat the earlier-seeming one as a backstop, not a plan.

Corporations and most other taxpayers (income tax)

For corporations and most other taxpayers, the deadline is a flat 90 days from the date on the notice of reassessment. There is no one-year alternative branch.

GST/HST objections

For GST/HST, the notice of objection must be filed within 90 days of the date of the assessment. The collection consequences for GST/HST are different and more aggressive than for income tax, which we cover in our guide on CRA collections, frozen accounts, and requirements to pay.

If you missed the deadline: the one-year extension

Missing the objection deadline is the single most consequential mistake a taxpayer can make, but it is not always fatal. The Income Tax Act provides a mechanism to apply for an extension of time to file a late objection.

Under section 166.1, you apply to the CRA for an extension. If the CRA refuses, or does not respond within 90 days, you can then apply to the Tax Court of Canada under section 166.2. Either way, the outer limit is firm: the application must be made within one year after the expiry of the original objection deadline. After that one-year window closes, there is no further remedy.

An extension is not granted just because you ask. You must show, among other things, that within the original deadline you were unable to act or to instruct someone to act for you, or that you genuinely intended to object; that it would be just and equitable to grant the application; that the application was made as soon as circumstances permitted; and that there are reasonable grounds for the objection. The CRA takes a strict view of late-filed extensions, so the supporting record matters. If you are reading this within a few weeks of any deadline, treat the file as urgent.

Step 1: Read the reassessment and identify the issues

Before you write anything, you need to understand exactly what the CRA changed and why. A reassessment is built on the CRA's assumptions of fact — the factual conclusions the auditor relied on to support the adjustments. Your objection has to engage those assumptions directly, because under Canadian tax law the CRA's assumptions of fact are presumed correct until the taxpayer rebuts them. You carry the burden. You cannot rebut an assumption you have not identified.

Many reassessments contain a long list of adjustments, but usually only a handful drive most of the dollar exposure. Part of preparing an objection is narrowing the file to the issues that actually move the needle, rather than scattering your energy across every line.

Step 2: Gather your documents

An objection is, fundamentally, an evidentiary exercise. Most tax disputes turn on the facts, most facts turn on the documents, and the document record is what persuades an Appeals officer. The materials you will typically want include:

the notice of reassessment (and notice of confirmation, if one was issued);
the original audit query letters and your responses;
the proposal letter and your response, if any;
the T1 or T2 returns for the years under reassessment;
financial statements, general ledgers, and trial balances;
bank statements for the relevant personal and business accounts;
source documents for the disputed transactions;
corporate records — minute book, articles, share registers, resolutions, and any reorganization elections;
any prior CRA correspondence, valuations, or expert reports relevant to the reassessment.

Where the file is large, it is often worth obtaining the CRA's own audit working papers and the auditor's log (the T2020 or its equivalent) so you can see precisely how the auditor reached the numbers.

Step 3: Prepare the objection — Form T400A and the submissions

The CRA's standard income-tax objection form is Form T400A, Notice of Objection (Income Tax Act). You can also object in writing without the form, or, for many individuals, through the "Register my formal dispute" service in CRA My Account. For GST/HST, the parallel form is Form GST159.

But filing a bare T400A with a single line of disagreement is the minimum, not a strategy. A persuasive objection is a written legal document that:

states the issues clearly and concisely;
states the facts in an organized chronology;
sets out the law and applies it to the facts;
attaches the supporting documents as labelled exhibits; and
asks for specific relief — full vacating of the reassessment, a partial reduction, removal of penalties, recharacterization of an amount, or some combination.

A word of caution: statements you make in an objection can be relied on later at the Tax Court. Be deliberate about what you concede. Do not give away a factual point that would be better left for trial, and do not overstate a position you cannot ultimately support with evidence.

Step 4: The large-corporation rules

If the taxpayer is a "large corporation" — broadly, a corporation with taxable capital employed in Canada above the threshold in the Income Tax Act — there is a critical additional requirement under subsection 165(1.11). A large corporation's objection must:

reasonably describe each issue to be decided;
specify, for each issue, the relief sought as a dollar amount; and
provide the facts and reasons the corporation relies on for each issue.

This is not a formality. Under the large-corporation rules, a corporation is generally locked into the issues and the quantum it raised in the objection. If an issue or an amount is left out of the objection, the corporation can be barred from raising it later at the Tax Court. For large corporations, the objection effectively defines the entire scope of the dispute going forward, so it has to be drafted comprehensively from the outset.

Step 5: Filing — how and where

You can file an income-tax objection electronically through CRA My Account or My Business Account, by mail or fax to the designated Chief of Appeals at your CRA Appeals Intake Centre, or in person. Whatever method you choose, keep proof of the filing date. Because the deadline is calculated to the day, a date stamp, a confirmation number, or a fax transmission report can become important if the CRA later questions timeliness.

What happens at Appeals

Once filed, your objection is assigned to a CRA Appeals officer. The Appeals process generally unfolds like this:

Acknowledgement and assignment. The CRA acknowledges receipt and, in time, assigns an Appeals officer. Wait times vary widely with the CRA's backlog.
Independent review. The Appeals officer reviews the audit file and your submissions afresh. This is a genuine second look, not a rubber stamp of the auditor's work.
Information requests and submissions. The officer may ask for additional documents or explanations. Responding promptly and thoroughly, and requesting a meeting where the file warrants it, keeps the dialogue productive.
Settlement. Appeals officers can settle within their authority on a principled basis. Many objections resolve through a partial settlement — for example, conceding some adjustments while reversing the ones that are genuinely wrong.
The decision. The CRA issues a notice of confirmation (the reassessment stands), a notice of reassessment (the reassessment is varied in your favour, in whole or in part), or vacates the reassessment entirely.

How long does it take? A simple objection can resolve in six to nine months. A complex objection involving large amounts or multiple years frequently takes 12 to 24 months, and some files sit at Appeals far longer.

Can the CRA collect while my objection is pending?

For most income-tax debts, the CRA's collection action is generally restricted while a notice of objection is under consideration and during the related appeal period. That restriction does not apply to every category — GST/HST, source deductions, large-corporation amounts (where only half the amount is held back), and certain other debts can still be collected while you object. Because the answer depends on the tax type, this is worth confirming for your specific file. We go deeper on collection powers and how they interact with objections in our guide to CRA collections.

If the objection is confirmed

If the CRA confirms the reassessment, the next step is an appeal to the Tax Court of Canada, which must be filed within 90 days of the date on the notice of confirmation. The objection and the appeal are two different proceedings with different rules and a different forum. To understand how they fit together — and when you can skip ahead to court — see our companion guide, Notice of Objection vs Tax Court Appeal: Which Path and When. For the mechanics of the litigation itself, see The Tax Court of Canada Appeal Process.

Common mistakes when filing an objection

Missing the deadline. Statutory and unforgiving. Calculate it the day the reassessment arrives.
Filing a bare form with no substance. A one-line T400A is rarely persuasive. The submissions are the objection.
Disputing everything. Appeals officers respond better to a focused argument on the issues that drive the dollars than to a blanket denial.
Ignoring the CRA's assumptions of fact. You cannot rebut what you have not identified.
Conceding facts that belong at trial. Objection statements can be used against you later.
Forgetting penalties. Gross-negligence penalties under subsection 163(2) are often added almost automatically and can be challenged as a separate ground.
Producing a loose pile of paper. Organized, labelled exhibits with a coherent narrative persuade; an unstructured document dump does not.

Do you need a lawyer to file an objection?

The objection process does not require legal representation, and for small, narrow files self-representation is sometimes appropriate. For larger files — those involving significant dollars, gross-negligence or third-party penalties, complex legal issues, or substantial evidentiary questions — experienced representation generally produces better outcomes, in part because the way an objection is framed shapes everything that follows it, including any eventual Tax Court appeal.

Barrett Tax Law prepares and files notices of objection, makes written and oral submissions to the CRA Appeals Division, and represents clients through settlement negotiation and, where necessary, the appeal to the Tax Court of Canada. You can read more about that work on our tax disputes and objections page, and if penalties are part of your file, our taxpayer relief application page explains the separate route to having interest and penalties reduced.

How to File a Notice of Objection (Step by Step)