How to dispute a CRA assessment
Objections to assessment
Section 165 gives you the right to formally object to a CRA assessment or reassessment within 90 days of the date of the notice, and establishes the dispute resolution process.
Plain-language explanation
Section 165 is your first step in disputing a CRA tax decision. If CRA assesses you incorrectly, you can file a Notice of Objection to formally challenge it.
Filing deadline: For individuals, the objection must be filed within: - 90 days of the date of mailing of the notice of assessment/reassessment, OR - 1 year from the tax return due date (whichever is later)
How to file: File Form T400A (Notice of Objection) by mail to the Chief of Appeals at your tax services office, or use CRA My Account online. Include the assessment number, the year, what you disagree with, the facts and reasons.
What happens next: CRA's Appeals Division (independent of Audit) reviews your objection. They may: - Confirm the assessment (you're right, they won't change it) - Vary the assessment (partial agreement) - Vacate the assessment (they agree with you)
Tax stays collectible: Filing an objection does not stop CRA from collecting the assessed tax. You can request a collection stay, but CRA may or may not grant it for the objected amount.
If objection is denied — Tax Court: If the objection is denied or not decided within 90 days, you can appeal to the Tax Court of Canada under s.169.
Example
CRA audited Ana and added $25,000 to her income, claiming a deduction was not allowed. CRA issues a reassessment on March 15, 2026. Ana has until June 13, 2026 (90 days) to file a Notice of Objection with CRA Appeals.
Amendment history
Significant changes to this provision. Older versions help you understand rules that applied in prior tax years.
CRA introduced a new online objection filing process through My Account and My Business Account, simplifying the T400A process.
Before
Objections required paper T400A filed by mail to CRA Chief of Appeals
After
Online filing via CRA My Account available in addition to paper filing
Budget 2022 proposed measures to improve CRA appeal timelines and reduce the objection backlog, which had grown significantly during COVID. CRA committed to processing objections within 18 months.
Before
Objections often took 3–5 years to resolve with no statutory deadline for CRA to respond
After
Service standards set; after 90 days without CRA decision, taxpayer can appeal directly to Tax Court under s.169
Common questions
How long do I have to object to a CRA assessment? +
90 days from the date shown on the notice of assessment or reassessment. For individual income tax, you can file up to 1 year after the due date of the return if that is later. Missing the deadline forfeits your right to object — act promptly.
Is filing an objection free? +
Yes. Filing a Notice of Objection with CRA is free. If you escalate to the Tax Court (s.169), the Informal Procedure (for amounts under $25,000 per year) is also low-cost and does not require a lawyer.
What if CRA doesn't respond to my objection? +
If CRA hasn't decided your objection within 90 days, you can bypass CRA and file a Tax Court appeal directly under s.169. You can also wait — there is no absolute deadline on CRA to respond, but you can always proceed to Tax Court.
Key terms
Related sections
Related guides
CPA recommendation
A CPA or tax lawyer specializing in CRA disputes can help you prepare a strong objection. The Appeals Division is genuinely independent — well-documented objections succeed regularly.
Source: Income Tax Act, RSC 1985, c. 1 (5th Supp.), section 165. — Read the official text on Justice Canada
These summaries are for educational purposes only and do not constitute legal or tax advice. Speak with a CPA for advice on your specific situation.