If you do not agree with your income tax Notice of Assessment, the first step would be to call Canada Revenue Agency (CRA) to discuss the situation, and see if it can be easily resolved. See the CRA Contact Information including toll-free telephone numbers and approximate wait times.
If this does not work, you can file a notice of objection. This can be done by writing a letter to the Chief of Appeals at your tax services office, or by filing form T400A Objection - Income Tax Act.
There are time limits for filing a notice of objection.
For individuals or a graduated rate estate, the time limit is the later of:
If the assessment is for taxes on over-contributions to an RRSP or TFSA, an objection must be filed within 90 days from the date of the notice of assessment or determination. This also applies to loss determination cases.
For corporations, the notice of objection must be filed within 90 days from the mailing date of the Notice of Assessment.
According to the Income Tax Audit Manual s. 19.2.1 Time period to file an election, if certain conditions are met, a taxpayer may apply to either the Minister or the Tax Court for an extension of the time to file an objection. See Time limit for requesting an extension in P148 Resolving your dispute: Objection rights under the Income Tax Act.
The timing of filing the notice of objection is very important, even if a CRA agent implies that it is not important - see the August 2023 Life in the Tax Lane video which discusses a Tax Court Case about this, and the May 2026 Life in the Tax Lane video.
After your notice of objection is filed, the Minister of National Revenue will notify you that it is:
Tax Tip: Get professional advice!
File an objection - Income tax
Income tax objections decision tree
P148 Resolving Your Dispute: Objections and Appeal Rights Under the Income Tax Act - this pamphlet includes a sample Notice of Objection letter, and instructions on what information to include.
Your Rights as a Taxpayer - Taxpayer Bill of Rights / Taxpayers' Ombudsperson