How to Amend Your Tax Return After Filing with the CRA

If you've already filed your 2026 tax return and realize you made a mistake, there's good news: you can request changes without severe penalties if you act quickly. The CRA allows you to amend your return through a formal adjustment request, and the process is straightforward whether you filed online or by mail. The key is being proactive, honest about the error, and following the CRA's specific procedures to update your records. People request adjustments for many reasons. You might have forgotten to report income, missed a deduction, claimed a credit incorrectly, or discovered a calculation error after filing. Common scenarios include: Receiving a T4 or T5 slip after you filed Realizing you missed eligible medical expenses Forgetting to claim RRSP contributions or investment losses Incorrectly claiming or missing spousal or dependent credits Discovering you were eligible for a credit you didn't know about The CRA won't automatically correct these errors for you, so submitting an amendment request is essential to ensure your tax record is accurate. You can request an adjustment at any time, but the CRA has time limits for how far back they'll consider changes.

Frequently Asked Questions

How far back can I amend my tax return with the CRA?

You can request adjustments for the current tax year and the previous three calendar years. For example, in 2026, you can amend returns from 2025, 2024, 2023, and 2022. Going further back requires written approval from the CRA.

Do I have to pay penalties if I found an error and amend my return?

Penalties may apply if you owed more tax, but they are often waived if you voluntarily report the error before the CRA discovers it. Interest will be calculated on any unpaid amount from the original due date.

Can I amend my 2026 tax return online through CRA My Account?

Yes, for simple adjustments involving basic income or deduction changes, you may use CRA My Account. However, complex changes require submitting Form T1-ADJ by mail or through a NETFILE-authorized representative.

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

Simple adjustments typically process in 2-4 weeks, while more complex ones can take 6-8 weeks or longer. You'll receive a notice of assessment once the review is complete.

What documents do I need to submit with my amendment request?

Submit receipts, T-slips, bank statements, and any other proof supporting your changes. Include a clear written explanation of what you're amending and why, along with a completed Form T1-ADJ.

Steps

1. Identify the error on your filed return: Review your notice of assessment and any documentation you filed with. Pinpoint exactly what was missed or calculated incorrectly (income, deductions, credits, etc.).
2. Gather supporting documentation: Collect all receipts, T-slips, bank statements, and proof that supports your amendment. Organize these clearly so the CRA can quickly verify your claim.
3. Choose your amendment method: Decide whether to use CRA My Account (for simple changes), mail Form T1-ADJ, call the CRA, or work with a NETFILE representative. Simple adjustments are fastest online; complex ones should be mailed with full documentation.
4. Complete Form T1-ADJ if mailing: Fill out the Request for Adjustment form clearly, listing each change and its reason. Write a brief cover letter explaining the amendment and attach all supporting documents as copies.
5. Submit your amendment request: Mail Form T1-ADJ to your local CRA tax center, or submit through My Account or a representative. Keep a copy of everything you send for your records.
6. Wait for the CRA to process: Monitor the status through CRA My Account if possible. The CRA will send you a new notice of assessment once the adjustment is complete, which typically takes 2-8 weeks.