How to Formally Dispute a CRA Notice of Reassessment for Your Small Business

Receiving a notice of reassessment from the CRA can be unsettling, especially when the adjustments increase tax owing or reduce refundable credits. The first thing to know is that a reassessment is not the final word. You have a formal right to dispute it, and the process is designed to give your business a fair second look—provided you understand the deadlines and put together a clear, factual case.

In this guide, we walk through how to formally dispute a CRA notice of reassessment for your small business, from the initial review of the notice to the steps after filing an objection. We focus on the practical details that matter most: the 90-day window, what to include in your objection, and how to track the case as it moves through the CRA appeals process.

Understanding the CRA Notice of Reassessment

A notice of reassessment is issued when the CRA reviews your filed tax return and changes one or more amounts. This can happen because the agency found an error, received new information such as a missed slip, or completed an audit. The notice typically shows the original amounts, the revised amounts, and a short explanation of what changed.

Before you react, compare the reassessment to your own records line by line. Identify exactly which income item, expense, deduction, or credit was adjusted. Ask yourself whether the CRA’s position could be correct—sometimes the agency catches legitimate mistakes. If you still disagree after a careful review, note the specific points of contention. Those points will form the backbone of your objection.

Exploring Alternatives Before You Formally Dispute a CRA Notice of Reassessment

Informal resolution with the CRA

Before filing a formal objection, it is often worth contacting the CRA directly. If the change resulted from a misunderstanding or missing information, a phone call or written explanation may resolve the issue without a formal dispute. The CRA encourages taxpayers to discuss the matter first, and many discrepancies are corrected through this route.

Requesting an adjustment

If you discover an error in your original return—or have new documents that support a different position—you can request an adjustment instead of filing an objection. When the CRA processes that request, it will issue a new notice of reassessment. If you still disagree with that new notice, the 90-day objection clock starts again from the date of the new reassessment. This can be a lower-effort path when the issue is a simple correction rather than a dispute over the interpretation of law.

Your Right to Formally Dispute a CRA Notice of Reassessment

Under the Income Tax Act, you have a legal right to object to any assessment or reassessment if you believe the CRA misinterpreted the facts or applied the law incorrectly. This right covers the amount of tax, interest, and penalties. Filing a notice of objection is the formal way to put your disagreement on record. It triggers a review by a separate appeals division, independent from the original assessing area.

Filing an objection does not mean you automatically win, but it protects your ability to argue the case and, if necessary, escalate it to the Tax Court of Canada. Without a timely objection, the reassessment becomes final and much harder to challenge.

Critical Deadlines: 90-Day Rule and Extension Requests

The 90-day deadline

In most cases, you have exactly 90 days from the date printed on the notice of reassessment to file your objection. This deadline is strict. Mark it on your calendar as soon as the notice arrives. If the 90th day falls on a weekend or holiday, the deadline may extend to the next business day, but you should not rely on that buffer.

How to request an extension

If you miss the 90-day deadline, you can apply for an extension. The request must be made within one year after the original 90-day deadline expired. You can submit the extension request at the same time as your late-filed objection. In your request, explain why you missed the deadline—for example, serious illness, a death in the family, or other circumstances beyond your control—and show that you acted as soon as possible. The CRA does not grant extensions automatically; it must be satisfied that the delay was justified and that granting the extension would be fair.

Crafting a Strong Notice of Objection: Facts, Reasons, and Supporting Documents

Gathering supporting documents

Your objection is only as strong as the evidence behind it. Collect every document that supports your position: receipts, contracts, bank statements, correspondence with the CRA, and any other records that explain the amounts in question. Organize the documents by issue so the appeals officer can quickly connect each piece of evidence to your argument.

Structuring your statement of facts and reasons

A bare form that simply says “I disagree” is rarely persuasive and can limit your options later. Instead, for each issue you are disputing, provide a clear factual summary, explain why the CRA’s adjustment is incorrect, and state the relief you are requesting. If you omit an issue at this stage, you may not be able to raise it later in a Tax Court appeal. Be specific about amounts, dates, and the legal or factual basis for your position.

Our team has practical experience resolving CRA reviews and audits on GST/HST and corporate tax matters, which helps us focus on the specific issues in a notice of reassessment.

How to File Your Notice of Objection: Online and Mail Options

Filing online via CRA My Business Account

The fastest way to file is through the CRA’s online services. Log in to My Business Account, select “File a formal dispute (Notice of Objection),” and follow the prompts. You will need to identify the reassessment you are disputing and enter the details of your disagreement. Once submitted, you receive a case number instantly. Use that case number whenever you send supporting documents or contact the CRA about the case.

Filing by mail or fax using Form T400A

If you prefer paper, download Form T400A, Notice of Objection – Income Tax Act, from the CRA website. Fill it out completely, attach copies of all supporting documents, and mail or fax it to the Appeals Intake Centre for your region. Keep a copy of everything you send and note the date of mailing or fax confirmation. Missing the correct address can delay processing, so double-check the current Appeals Intake Centre information before sending.

Using CRA Online Tools to Track Your Objection

After filing, you can monitor the status of your objection through My Business Account or Represent a Client. The CRA’s online portal shows processing times, complexity level, and any correspondence issued in your case. You can also use the “Submit Docs” service to upload additional documents electronically. Track your case number and check for updates regularly; this reduces the risk of missing a request for information from the appeals officer.

What Happens After Filing: The CRA Appeals Process

Review by an Appeals Officer

Once your objection is received, it is assigned to an appeals officer who was not involved in the original assessment or audit. The officer’s job is to conduct an impartial review of the file, consider your arguments and evidence, and try to resolve the dispute. They may agree with your position, propose a settlement, or confirm the reassessment.

Possible interactions and information requests

During the review, the appeals officer may contact you or your authorized representative to ask questions or request additional information. Respond promptly and keep a written record of all communications. If you fail to provide requested material, the officer may proceed based on the information already on file, which could hurt your case. Be prepared to explain your position clearly and provide any missing documents.

Payment of Disputed Amounts During the Dispute

For small businesses, you generally do not have to pay the amount of tax, interest, or penalty that is under dispute while the objection or appeal is being reviewed. However, normal interest continues to accrue on any outstanding balance from the original balance-due day. If you lose the dispute, you will owe the tax plus accumulated interest. Amounts that are not in dispute still must be paid on time. If you cannot pay the undisputed portion, contact the CRA to discuss payment arrangements separately.

If the Objection Is Unsuccessful: Appealing to the Tax Court of Canada

Filing an appeal to the Tax Court

If the appeals officer confirms the reassessment and you still believe the CRA is wrong, the next step is to appeal to the Tax Court of Canada. This is a more formal legal process. You will need to file a notice of appeal with the court and serve the CRA, following the court’s rules and deadlines. The Tax Court will consider the evidence and arguments from both sides and issue a binding decision.

Deadlines and procedures

The Tax Court has its own filing deadlines and case management procedures. You generally cannot raise new issues that were not included in your original notice of objection, which is why a thorough objection matters. At the Tax Court stage, legal representation often becomes important because the process involves court documents, evidence rules, and potential hearings. If you are considering an appeal, seek guidance promptly to avoid missing a court deadline.

If you have received a notice of reassessment and want help assessing the adjustments, preparing an objection, or understanding your next steps, contact us to discuss your situation. We can help you decide the best path forward and work with you to protect your rights.

For simple corrections, our corporate tax adjustment process walkthrough covers how to amend a T2 and what the CRA does next.