How to File an Objection to a CRA Income Tax Assessment or Reassessment

How long do you have to object to a CRA assessment?

The deadline depends on the taxpayer and the type of assessment. Under the Income Tax Act, an individual other than a trust, or a graduated rate estate, generally has until the later of:

• one year after the filing-due date for the tax return; or
• 90 days after the date of the notice of assessment or determination, subject to the rules that apply to the particular determination.

For corporations, the objection deadline is generally 90 days from the date of the notice of assessment or determination. In other cases, including certain loss determinations and assessments of tax relating to RRSP or TFSA over-contributions, the CRA states that the deadline is generally 90 days.

Do not assume that contacting the CRA informally stops the objection deadline. If you want to preserve formal dispute rights, check the deadline shown by the applicable rules and file the objection on time.

How to file the objection with the CRA

The CRA accepts income tax objections through its secure portals and by paper submission. Filing through a secure portal can allow the objection to reach the CRA's Appeals process sooner.

Option 1: File online

Individuals can sign in to CRA My Account and use the service for registering a formal dispute. Businesses can use My Business Account where applicable, while authorized representatives can use Represent a Client.

When an objection is registered online, the CRA provides a case number. Keep it and use it when submitting supporting documents or corresponding about the dispute.

Option 2: Use Form T400A or a letter

You can complete Form T400A, Notice of Objection – Income Tax Act, and send it to the Chief of Appeals at the appropriate Appeals Intake Centre by mail or fax.

The CRA also accepts a signed letter that clearly explains the facts and reasons for the objection. A paper objection should contain enough information for the CRA to identify the taxpayer, assessment and disputed issues.

What to include in your Notice of Objection

The CRA says an objection should include:

• your name and complete mailing address;
• a daytime telephone number;
• the date of the notice of assessment;
• the tax year involved;
• your SIN, Business Number, trust account number or other applicable account number;
• the relevant facts and reasons for your objection;
• copies of supporting documents; and
• your representative's name and address, if applicable.

The objection must be signed and dated when a signature is required. For a corporation or trust, the CRA states that an authorized officer must sign.

Do you need an objection or simply a tax return adjustment?

A Notice of Objection is intended for a formal dispute about an assessment or determination. If you simply discovered an error, omitted information or want to change something you originally reported, the CRA may instead direct you to the applicable process for changing a T1, T2 or T3 return.

Before filing, the CRA recommends reviewing the notice and contacting the agency if you do not understand why the assessment was issued. An informal discussion can resolve some misunderstandings, but it does not remove the need to respect the formal objection deadline.

What if you missed the objection deadline?

You may be able to request an extension of time to file an objection. The CRA says the extension application must be made as soon as possible and no later than one year after the original objection deadline.

You must explain why the objection was not filed on time and provide the objection itself. Among the statutory conditions, you must generally show that during the original objection period you were unable to object or have someone object for you, or that you intended to object; that granting the application would be just and equitable; and that you applied as soon as circumstances permitted.

An extension can be requested through the applicable CRA online account or in writing to the Chief of Appeals. The CRA will issue a written decision. If the extension request is refused, additional rights involving the Tax Court of Canada may apply.

What happens after you file the objection?

The CRA provides a case number and validates the objection. An Appeals officer then reviews the disputed assessment, the facts, the law and the supporting information. The CRA describes this as an impartial review.

If Appeals agrees with you in whole or in part, the CRA may adjust the return and issue a notice of reassessment or redetermination. If it disagrees, it may issue a notice confirming the assessment or determination.

Processing time depends heavily on complexity. CRA statistics published in 2026 show that income tax objections resolved in June 2026 averaged 127 days for low-complexity cases and 389 days for medium-complexity cases. High-complexity objections may take more than 690 days on average. These are reported averages, not guaranteed completion times.

Do you have to pay the disputed tax while objecting?

The CRA says it will normally postpone collection action on disputed amounts after an objection is filed until 90 days after it sends its decision. Important exceptions exist, including certain amounts that had to be withheld and remitted, jeopardy situations, tax-shelter donation disputes and rules for large corporations.

Interest can generally continue to accrue on unpaid amounts while a dispute is ongoing. Paying some or all of the disputed balance can therefore reduce interest if the assessment is ultimately upheld. If paying a CRA balance is the separate problem, see how to set up a CRA payment arrangement when you cannot pay your tax debt.

An objection challenges whether the assessment itself is correct. It is different from asking the CRA for discretionary relief from assessed penalties or interest. For that separate process, see how to ask the CRA to cancel or waive tax penalties and interest.

What if you disagree with the CRA Appeals decision?

If you disagree with the CRA's decision on the objection, you can generally appeal to the Tax Court of Canada. The CRA's P148 guide states that the Tax Court must receive the notice of appeal within 90 days from the date the CRA sends its decision, such as a notice of reassessment or notice of confirmation.

The guide also states that a taxpayer may appeal to the Tax Court if the CRA has not provided a decision on the objection within 90 days after the objection was filed. Court proceedings are a separate stage from the CRA objection itself and have their own procedural rules.

Common mistakes to avoid

• Missing the objection deadline while waiting for an informal CRA discussion or adjustment request.
• Filing before an assessment or determination has actually been issued.
• Sending only a statement that you disagree without explaining the relevant facts and reasons.
• Leaving out documents that support your position.
• Confusing an objection with a request to change information you voluntarily reported on the return.
• Confusing an objection with taxpayer relief. Penalty and interest relief is a separate process.
• Ignoring CRA correspondence or requests for additional information after the objection has been assigned.