SPECIAL TO THE GLOBE AND MAIL

PUBLISHED APRIL 8, 2026

Preparing a tax return each year can feel like a marathon. It can be a long process that tests your stamina. A good friend experienced identity theft last year, but said there was potentially a silver lining to it. “Tim, if I’m lucky, the thief will use my information to file my tax return for me. That’ll make it all worth it,” he said.

As painful as filing can be, it might only be the start of the marathon. If you’ve ever discovered a mistake after filing your return or have disagreed with the Canada Revenue Agency over an assessment, you’re not alone. Today, let’s look at three options you have if something is amiss.

Filing an adjustment

Suppose you’ve made a mistake on your tax return. Maybe you forgot a slip, missed a deduction, or entered something incorrectly. Don’t sweat it. You can file an adjustment.

The CRA allows you to request changes after you’ve received your Notice of Assessment. You can do this online through “Change my Return” in your CRA My Account, through ReFILE using tax software, or by completing Form T1-ADJ T1Adjustment Request, and mailing it in.

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The T1-ADJ is simple. You’ll identify the year you want to change, the specific line numbers being adjusted, and provide a brief explanation along with supporting documents. In most cases, you can request changes going back up to 10 years.

Now, before reaching for that form, CRA suggests you call them first. Some minor issues can be resolved with a conversation – assuming you can reach a person. No paperwork required.

One more point: Don’t file a second tax return for the same year. That’s not how the system works. Use the adjustment process instead and let the CRA make revisions.

Filing an objection

Sometimes the issue isn’t a simple error – it’s a disagreement with the CRA. This has become all too common. In the past, you could speak with a knowledgeable CRA employee who had the authority to resolve issues quickly. Today, that’s rare. Front-line agents often lack knowledge of our tax law and usually deny deductions, credits, or benefits by default.

If you think the CRA has misinterpreted the facts or applied the law incorrectly, and your conversations by phone go nowhere, your next step is to file a Notice of Objection. This is your formal way of saying “I think you got this wrong.”

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For individuals, the deadline to file is generally the later of 90 days from the date on your Notice of Assessment or one year after the tax filing deadline for the return in question. In some cases, you can request an extension, but this must be done within one year of the original objection deadline. For corporations, the deadline is typically 90 days from the date of the assessment.

You can file an objection online through My Account, by submitting Form T400A, or by sending a signed letter. Your submission should clearly outline the facts, the disputed issues, your reasons, and include supporting documentation.

The CRA’s Appeals Branch, which is separate from the original assessment team, will review your case. An appeals officer may contact you before making a decision. But be prepared to wait: The process can take anywhere from six months to two years, or longer for complex cases.

Filing an appeal

If you’ve gone through the objection process and still disagree with the outcome, the next step is to take the matter outside the CRA by filing an appeal with the Tax Court of Canada.

The Tax Court is independent, and at this stage your dispute becomes a legal matter rather than an administrative one. You don’t need a special form – just a written Notice of Appeal. It should include the relevant facts, your reasons for appealing, your contact information, and the date of the notice of confirmation or (re)assessment being challenged. You can file your appeal by mailing or delivering it to a Tax Court office, or by fax or electronic submission.

You’ll generally want a lawyer to represent you since formal rules of evidence and legal procedure will apply, unless you’re filing under the Tax Court’s “Informal Procedure.” The process can be used if the disputed federal tax and penalties are $25,000 or less per assessment, the disputed loss is $50,000 or less, or only interest is at issue. Even then, working with a lawyer or tax professional can improve your chances.

Timing is critical. You typically have 90 days from the date of the CRA’s decision on your objection to file your appeal. An extension may be allowed if you miss the deadline, but only within a limited time.

Once filed, the court will schedule a hearing, usually near where you live. Both sides present their case, and a judge issues a binding decision, which can be appealed to the Federal Court of Appeal.

Eventually, you’ll cross the finish line and the marathon will end.

Tim Cestnick, FCPA, FCA, CPA(IL), CFP, TEP, is an author, and co-founder and CEO of Our Family Office Inc. He can be reached at tim@ourfamilyoffice.ca

Download a copy of this article in pdf here.