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File a Notice of Objection with the CRA's Appeals Intake Centre for your province within 90 days of the date printed on your notice of assessment or reassessment. For income tax, use Form T400A; for GST/HST, Form GST159. The date you mail it counts as your filing date, so keep proof of postage. This is general information, not tax advice.
| Key fact | Details |
|---|---|
| What to file | A Notice of Objection: Form T400A for income tax, Form GST159 for GST/HST. Your objection must be in writing and state which parts of the assessment you dispute and why. |
| Deadline | 90 days from the date printed on the notice of assessment or reassessment, not from the day you opened it. |
| Where to send it | The CRA Appeals Intake Centre for your province, not your local tax centre. The CRA publishes the current intake centre addresses. |
| Proof of filing | The mailing date counts as your filing date. Send it by registered mail and keep the receipt. |
| Missed the deadline? | You can apply for an extension to file within one year of the original deadline. |
| Collection while you wait | For individual income-tax objections, the CRA generally holds off collecting the disputed amount while your objection is being decided. |
Specificity. The CRA needs to know exactly which lines of the assessment you dispute and the facts or law behind your position. "I disagree with the reassessment" is an objection, but a weak one; "the CRA disallowed the home-office expenses on line 22900, and here are the receipts and the calculation" is a strong one. Attach copies (not originals) of the documents that support your case, and keep a complete copy of everything you send. Appeals officers decide cases on the written record, so what you put in the envelope is your whole argument until the review.
For individual income-tax assessments, the CRA generally pauses collection on the disputed portion while an objection is in the system, so you're not forced to pay first and argue later. This doesn't apply to everything: GST/HST debts are treated differently, and interest keeps running on amounts that are eventually confirmed owing. If you're unsure whether the pause applies to your situation, that's a question for a tax professional before the deadline passes, not after.
The objection goes to a CRA appeals officer who reviews the file independently of the auditor who made the assessment. This takes time: appeals are measured in months, not weeks. The officer may ask for more documents or a written explanation of your position. Eventually you get a decision: the assessment stands, it's changed in your favour, or it's changed partially. If you still disagree, the next step is the Tax Court of Canada, which has its own deadlines and filing process.
Yes. The CRA accepts objections through My Account, and for many people that's the faster route with an instant confirmation. Mail still works fine and has one advantage online filing doesn't: the registered-mail receipt is physical proof of your filing date if there's ever a dispute about timing. Near the 90-day deadline, send the objection by registered mail rather than hoping a standard letter arrives in time.
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