How to Request a CRA Tax Return Adjustment for Previous Years in 2026

If you've discovered errors, missed deductions, or overlooked credits on a previous year's tax return, you can request a CRA adjustment to correct it. The CRA allows you to amend returns for up to 10 calendar years back, meaning you can go back to 2016 and earlier for the 2026 tax year. You'll need to submit a Form T1 Adjustment Request or file an amended return through your CRA My Account, depending on what you're changing and how far back the error goes. There are many common reasons why Canadian tax filers request adjustments: - You forgot to claim a tax credit you were eligible for - You had unreported income from investments or self-employment - You missed deductible expenses from a previous year - Your marital status changed and affects your credits retroactively - You discovered calculation errors on your original return - You received a T slip (T4, T5, T2202, etc.) late in the year after filing Even small changes can result in refunds or reduce what you owe, so it's worth reviewing past returns carefully. The CRA allows adjustment requests for returns filed in the last 10 calendar years.

Frequently Asked Questions

How far back can I request a CRA tax adjustment?

You can request adjustments to returns filed in the last 10 calendar years. For 2026, this means you can go back to 2016 and earlier. Some specific claims may have longer periods, so check the CRA website for your situation.

What's the difference between an adjustment request and filing an amended return?

An adjustment request (using Form T1-ADJ or CRA My Account) asks the CRA to change your return for you. An amended return is when you file a new return yourself. For most Canadians, submitting an adjustment request through the CRA is simpler and more common.

How long does it take the CRA to process an adjustment request?

Most adjustment requests take 4 to 6 months to process. You can track the status of your request through CRA My Account. The CRA will send you a Notice of Assessment once complete with your updated tax amount.

Can I request an adjustment if I'm currently in a CRA audit?

No, you cannot request an adjustment for a return that is currently under audit or dispute with the CRA. You must wait until the audit is resolved before you can make changes to that year's return.

What documents do I need to include with my adjustment request?

Include supporting evidence like T slips, receipts, invoices, and proof of income for the changes you're making. You don't need to mail original documents, but keep them for your records in case the CRA asks to verify your claim.

Steps

1. Gather your original documents and T slips: Collect all receipts, invoices, and tax forms related to the changes you want to make. This includes T4s, T5s, RRSP receipts, medical expenses, or donation records from the previous tax year you're adjusting.
2. Decide whether to use CRA My Account or Form T1-ADJ: For recent returns and simple changes, log into your CRA My Account and use the online adjustment tool. For older returns or complex adjustments, download and complete Form T1-ADJ from the CRA website.
3. Fill out your adjustment request with clear details: Clearly explain what you're changing, which tax year, and why. Include line numbers from your original return and the corrected amounts. Be specific about each change you're requesting.
4. Submit your request online or by mail: If using CRA My Account, submit directly through the portal and you'll receive an email confirmation. If mailing Form T1-ADJ, include supporting documents and send to your local tax centre address (found on the CRA website).
5. Track your adjustment status and wait for the Notice of Assessment: Monitor your request through CRA My Account. Once processed (typically 4-6 months), the CRA will send you a Notice of Assessment showing your updated tax owing or refund.