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CRA & compliance

How to dispute a CRA assessment: objections, deadlines, appeals

A notice of assessment is not always the last word. If you think the CRA misread the facts or applied the law incorrectly, there is a formal route to challenge it, and it has firm deadlines. Before you use it, work out whether you are disputing the CRA’s decision or fixing something on your own return. This article walks through the order of steps, the time limits, what happens to collection and where a Tax Court appeal fits.

Sora Accounting & Tax · General information · Editorial policy
Updated · 7 min read

From a notice of assessment to a possible Tax Court appeal

A flow from reading a notice of assessment, to a call or adjustment, a notice of objection, the CRA decision and an appeal to the Tax Court of Canada.

Visual labels: Call or adjust; Notice of objection; CRA decision; Tax Court appeal.

What to take away

  • Read the notice and note its date first, because most objection deadlines run from that date.
  • Call or request an adjustment before filing an objection where the issue is an error or missing information.
  • Interest generally keeps running while you dispute, and collection rules differ between income tax and GST/HST.

Start by reading the notice, not by filing

Find the date on the notice, the tax year or reporting period, and the explanation of what changed. Those three details drive almost every decision that follows: which deadline applies, which program issued it and what you would be arguing about. Keep the notice and any earlier letter together, with the working papers behind the original return.

Then decide what kind of disagreement you have. Sometimes the CRA is simply missing a slip, a receipt or a fact you did not give it. Sometimes you made the mistake. Sometimes you believe the CRA applied the rules wrongly to facts that are not in dispute. Each of these has a different best route, and mixing them up is the most common reason a dispute drags on.

Try a call or an adjustment request first, where it fits

The CRA’s own dispute guide says that if you disagree with an assessment, you should first call or write to discuss it, and that many disputes are resolved that way. Use the phone number printed on the notice, and have your account number and the notice in front of you. Ask the officer to explain how the amount was reached and which document or fact the decision relied on.

If the problem is something you left out or got wrong, such as a missed slip, an unclaimed expense or a figure you can now support, the usual route is an adjustment request to the return rather than an objection. Corporations and trusts have their own adjustment processes, so the right one depends on the return type. Do not assume that a call or an adjustment request extends the objection deadline. Note the date you would need to file by before you start.

Know the objection deadlines before you rely on them

For income tax, an individual who is not a trust (or a graduated rate estate) generally has until the later of two dates: one year after the filing due date for the return, or 90 days after the date of the notice of assessment. A corporation has 90 days from the date of the notice. The CRA says the 90-day limit alone applies in every other income tax case, including loss determinations, so check which rule fits your notice. GST/HST objections must also be filed within 90 days after the notice was sent.

If you miss the deadline, you can ask for an extension. For income tax, the CRA says you must apply as soon as possible and no later than one year after the date the objection was due. You also have to show that you could not object or have someone object for you, or that you intended to object, and that it would be fair to grant the request. An extension is a decision the CRA makes, not a right. A late objection with no extension can be treated as invalid.

How to file a notice of objection

The CRA says filing through its secure portals gets the objection assigned sooner. Individuals sign in to My Account, businesses use My Business Account, and an authorized representative uses Represent a Client; in each case you select the option to register a formal dispute. You receive a case number that you quote on everything you send afterwards. By mail or fax, income tax objections use Form T400A, or a signed letter setting out the facts and reasons, and GST/HST objections use Form GST159.

Include your name and address, a daytime phone number, the date of the notice, the tax year, your account number, the facts and reasons for the objection and copies of your supporting documents. The objection must be signed and dated. If you are disputing more than one assessment, each needs its own notice of objection, although one statement of facts can cover identical reasons. Say specifically what you think the correct result is, so the appeals officer knows what to review.

What happens to collection while you dispute

For income tax, the CRA says it normally postpones collection on the disputed amount until 90 days after it sends its decision. There are exceptions, such as amounts you were required to withhold and remit, and situations the law specifies, such as jeopardy. Large corporations must pay 50% of the disputed amount when they file. Interest generally keeps accruing on the amount owing while it is in dispute, and a full or partial payment reduces the interest charged.

GST/HST is different. The CRA’s GST/HST memorandum says it may try to collect the full amount even though you have objected, though it may postpone collection on conditions it sets. Separately, it must accept security in a satisfactory amount and form for the disputed amount, and no collection action is taken on that amount while security is in place. If the dispute is resolved in your favour, amounts collected are refunded with interest. Ask about security or a payment arrangement early, because a notice of objection alone is not a stop on collection for GST/HST.

Taxpayer relief is a different request

An objection argues that the assessment itself is wrong. A taxpayer relief request accepts the assessment but asks the CRA to cancel or waive penalties and interest because of circumstances such as a serious illness, a disaster, a service disruption, financial hardship or an action of the CRA. It uses its own process, and it is not a substitute for disputing the tax itself.

There is a look-back limit. For penalties, the CRA will consider a request only if it relates to a tax year or fiscal period ending in any of the 10 calendar years before the year you ask. For interest, only amounts that accrued in that window count. A reassessment issued under the taxpayer relief provisions cannot itself be objected to, so make your best case in the request.

Appealing to the Tax Court of Canada

After the CRA reviews an objection it issues a notice of reassessment, if it agrees in whole or in part, or a notice of confirmation. If you still disagree, you can appeal to the Tax Court of Canada, which is independent of the CRA. The Tax Court must receive your notice of appeal within 90 days of the date the CRA sent its decision. You can also appeal if the CRA has not decided within 90 days of an income tax objection, or within 180 days of a GST/HST objection.

The court has an informal procedure, which carries no filing fee, and a general procedure, which does and is based on the amount in dispute. The Tax Court sets the rules for each procedure, so check its guidance or ask a representative before choosing. Missing the appeal deadline means applying to the court for an extension. For income tax appeals, the CRA usually postpones collection until the court rules, but not for amounts an employer had to withhold and remit, and not for GST/HST.

What to bring and when to get help

Bring the notice, the original return or filing, the CRA’s earlier letters, the evidence that supports your position and a short timeline of what you told the CRA and when. Write down the objection deadline and any court deadline in your calendar. If the amount is large, the issue turns on interpretation or the dispute involves a corporation or GST/HST, a professional can help present the facts and reasons in a form an appeals officer can act on.

For a first reply to a letter, see our guide to what to do after a CRA letter. If you want help working out whether to adjust, object or ask for relief, describe the notice to Sora so the work can be scoped around the dates and records involved. This article is general information and does not replace advice on your situation.

Sources & editorial notes

Sources checked October 24, 2026. The examples are illustrative and provide general information. Discuss how the guidance applies to your circumstances with your accountant.

Rules and guidance can change. Use the current official source and confirm the treatment for your facts. To flag an error, contact Sora.