---
title: "How to Amend a Tax Return in Canada: Fixing Mistakes After Filing"
id: "18476"
type: "post"
slug: "how-to-amend-tax-return-canada-2"
published_at: "2026-11-15T08:32:49+00:00"
modified_at: "2026-11-15T08:33:24+00:00"
url: "https://taxccount.com/blog/how-to-amend-tax-return-canada-2/"
markdown_url: "https://taxccount.com/blog/how-to-amend-tax-return-canada-2.md"
excerpt: "Mistakes happen. Maybe you forgot to claim a deduction, received a T4 after you already filed, or realized you entered the wrong number. The good news is that you can fix errors on a filed tax return in Canada without..."
taxonomy_category:
  - "Taxccount"
---

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[November 15, 2026](https://taxccount.com/blog/2026/11/)

# How to Amend a Tax Return in Canada: Fixing Mistakes After Filing

Mistakes happen. Maybe you forgot to claim a deduction, received a T4 after you already filed, or realized you entered the wrong number. The good news is that you can fix errors on a filed tax return in Canada without starting from scratch.

The Canada Revenue Agency (CRA) allows you to request changes to a return through a simple amendment process. This guide walks you through exactly how to do it.

Table of Contents

[Toggle](#)

## 1. Can You Change a Tax Return After Filing?

Yes. You can ask the CRA to change (amend) a tax return that has already been filed and assessed. You cannot simply re-file a new return — you need to submit a formal amendment request.

Important: Wait until your return has been assessed (you have received your Notice of Assessment) before submitting an amendment. Trying to amend before assessment can cause delays.

## Need to fix your tax return

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## 2. Common Reasons to Amend a Return

People amend returns for many reasons:

- Received a missing T4, T5, T3, or other slip after filing
- Forgot to claim a deduction (RRSP, childcare, medical expenses, etc.)
- Made a math or data entry error
- Need to correct an address or direct deposit information
- Missed claiming a tax credit
- Employer issued a corrected T4
- Want to carry back a capital loss from a later year
- CRA reassessed and you want to dispute or accept the change

## 3. How to Amend a Return: Two Methods

The CRA offers two ways to amend a filed return:

1. Online through CRA My Account (fastest)

2. By mail using Form T1-ADJ (Adjustment Request)

You cannot amend by calling the CRA. Amendments must be submitted in writing or online.

## 4. Method 1: Using CRA My Account Online

This is the easiest and fastest method.

**Step 1:** Log in to your CRA My Account at canada.ca/my-cra-account.

**Step 2:** Under the section for your income taxes, select the tax year you want to change.

**Step 3:** Click on the option to request a change to your return.

**Step 4:** Select the line(s) you want to change and enter the new amounts.

**Step 5:** Provide a brief explanation of why you are making the change.

**Step 6:** Submit. The CRA will confirm receipt and process the request.

Online amendment requests are typically processed within 2 weeks.

## 5. Method 2: Sending a T1-ADJ Form by Mail

If you prefer paper or do not have access to CRA My Account, you can mail in a T1-ADJ form.

**Step 1:** Download Form T1-ADJ (T1 Adjustment Request) from the CRA website.

**Step 2:** Fill in your name, social insurance number (SIN), address, and the tax year you want to amend.

**Step 3:** Identify the line numbers you want to change and provide the new amounts.

**Step 4:** Explain the reason for each change.

**Step 5:** Attach supporting documents (receipts, corrected slips, etc.).

**Step 6:** Sign and mail it to your local tax centre.

Paper amendment requests take longer to process — typically 8 weeks or more.

## 6. What Happens After You Submit the Amendment?

Once the CRA reviews your amendment request, it will issue a Notice of Reassessment. This document shows:

- Whether the CRA accepted your changes
- The revised amounts
- Whether you are owed an additional refund or now owe more tax

If additional tax is owed, interest will be charged from the original tax due date until the date of payment. There is generally no penalty for voluntarily amending a return to pay more tax, as long as the CRA has not already started an audit or investigation.

## 7. How Far Back Can You Amend a Return?

For most Canadians, you can request changes to your return for up to 10 years after the end of the tax year. For example, you could amend a return filed several years ago if you discover a missed deduction.

However:

- Amendments that result in money back to you can generally go back 10 years
- Amendments where you owe more tax may be limited to the normal reassessment period (usually 3 years from the date of your original assessment)

Think of the 10-year window as mostly for recovering refunds or credits you missed.

## 8. What If the CRA Owes You More Money?

If your amendment results in the CRA owing you more money (for example, you claimed a missed deduction), the CRA will send you an additional refund after processing the amendment.

If the original return was filed more than 3 years ago, the CRA can still refund you the difference for certain types of claims. Contact the CRA or a tax professional if you are unsure about the time limit for your specific situation.

## 9. What If You Owe the CRA More?

If your amendment results in more tax owing, you should pay the balance as soon as possible to minimize interest charges.

Interest on unpaid taxes is charged from the original due date (April 30 for most filers), not from the date of the amendment. So if you discover an error from three years ago, interest may have been accruing since then.

The good news is that voluntarily amending a return generally does not trigger penalties — only interest on the balance owing.

## Table of Summary

| Topic | Key Information |
| --- | --- |
| Can You Change a Tax Return After Filing? | Yes. You can request an amendment to a tax return that has already been filed and assessed. You cannot simply submit a new return; you must make a formal amendment request to the CRA. |
| Wait for Your Notice of Assessment | Wait until the CRA assesses your original return and issues your Notice of Assessment before requesting changes. Submitting an amendment before assessment can cause delays. |
| Missing Income Slips | You may need to amend your return if you receive a missing T4, T5, T3, or another income slip after filing. |
| Forgotten Deductions | Amendments can be used to claim deductions you missed, including RRSP contributions, childcare expenses, and medical expenses. |
| Incorrect Information or Calculations | You can correct mathematical mistakes, data-entry errors, or incorrect amounts entered on your original return. |
| Missed Tax Credits | You can amend your return to claim eligible tax credits that were overlooked when filing. |
| Corrected T4 Slips | If your employer issues a corrected T4 after you file, you may need to update your tax return. |
| Address or Direct Deposit Changes | You can request corrections to your address or direct deposit information through the appropriate CRA account services. |
| Capital Loss Carryback | You may amend a previous return to apply a capital loss from a later year, where eligible. |
| CRA Reassessment Changes | If the CRA reassesses your return, you may need to request an adjustment or dispute the changes, depending on your situation. |
| Two Ways to Amend a Tax Return | The CRA provides two methods: online through CRA My Account or by mail using Form T1-ADJ (T1 Adjustment Request). |
| Can You Amend by Calling the CRA? | No. You cannot amend a tax return by calling the CRA. Amendment requests must be submitted online or in writing. |
| Method 1: CRA My Account | Online amendments are the easiest and fastest option for taxpayers who have access to CRA My Account. |
| Step 1: Log In | Visit canada.ca/my-cra-account and log in to your CRA My Account. |
| Step 2: Select the Tax Year | Under the income tax section, choose the tax year you want to change. |
| Step 3: Request a Change | Select the option to request a change to your tax return. |
| Step 4: Enter Corrected Amounts | Select the tax line or lines that need changing and enter the correct amounts. |
| Step 5: Explain the Changes | Provide a brief explanation describing why you are requesting the amendment. |
| Step 6: Submit the Request | Submit the amendment. The CRA will confirm receipt and process the request. |
| Online Amendment Processing Time | Online amendment requests are typically processed within 2 weeks. |
| Method 2: Form T1-ADJ by Mail | Taxpayers who prefer paper submissions or cannot access CRA My Account can request adjustments by mailing Form T1-ADJ. |
| Step 1: Download Form T1-ADJ | Download the T1 Adjustment Request form from the CRA website. |
| Step 2: Enter Personal Details | Provide your name, social insurance number (SIN), address, and the tax year being amended. |
| Step 3: Identify Changes | Enter the tax line numbers that need correction and provide the revised amounts. |
| Step 4: Explain Each Change | Include an explanation for every adjustment requested. |
| Step 5: Attach Supporting Documents | Include relevant supporting documents, such as receipts or corrected income slips. |
| Step 6: Mail the Form | Sign the completed form and mail it to your local tax centre. |
| Paper Amendment Processing Time | Paper amendment requests typically take 8 weeks or more, making them slower than online submissions. |
| Notice of Reassessment | After reviewing an amendment, the CRA issues a Notice of Reassessment showing whether the changes were accepted, the revised amounts, and whether you are owed an additional refund or owe more tax. |
| Interest on Additional Tax Owing | If an amendment increases your tax payable, interest is charged from the original tax due date until the balance is paid. |
| Penalty for Voluntary Amendments | There is generally no penalty for voluntarily correcting a return that results in additional tax, provided the CRA has not already started an audit or investigation. |
| How Far Back Can You Amend? | Most Canadians can request changes for up to 10 years after the end of the tax year. The applicable time limit depends on the type of adjustment. |
| Amendments Resulting in a Refund | Requests that result in additional money back can generally go back 10 years, allowing taxpayers to recover certain missed deductions or credits. |
| Amendments Resulting in More Tax Owing | Adjustments that increase tax payable may be limited by the normal reassessment period, usually 3 years from the date of the original assessment. |
| What If the CRA Owes You More Money? | If an amendment identifies an additional deduction or credit, the CRA may issue an additional refund after processing the request. |
| Older Returns and Additional Refunds | The CRA may still refund certain amounts when the original return was filed more than 3 years ago. Contact the CRA or a tax professional to confirm the applicable time limit. |
| What If You Owe the CRA More? | Pay the additional tax as soon as possible to minimize interest charges. Interest generally applies from the original tax payment deadline, not the amendment date. |
| Original Tax Payment Deadline | For most taxpayers, the original tax payment due date is April 30. Interest may accumulate from that date if additional tax remains unpaid. |
| Can You Amend Before Assessment? | No. You should wait until you receive your Notice of Assessment before submitting an amendment request. |
| Can You Amend Multiple Years? | Yes. You can request changes for multiple tax years, but each year requires a separate amendment request. |
| Are Receipts Required for Online Amendments? | Receipts are not always required when submitting an online amendment, but the CRA may request supporting documents. Keep relevant records ready. |
| What If the CRA Rejects an Amendment? | The CRA will explain the reason for rejecting the request in a letter. If you disagree with the decision, you can file a Notice of Objection. |
| Conclusion: Correct Your Tax Return | The CRA allows taxpayers to correct filed returns through CRA My Account or by mailing Form T1-ADJ. Amendments can address missing slips, overlooked deductions, tax credits, and other errors. |
| Conclusion: Choose the Faster Method | CRA My Account is generally the quickest and easiest option, with online amendments typically processed within 2 weeks. |
| Professional Tax Assistance | A tax professional can review your return, determine whether an amendment is necessary, and help prepare and submit the adjustment correctly. |

## Frequently Asked Questions

### Can I amend a return before it has been assessed?

No. Wait until you receive your Notice of Assessment before submitting an amendment. The CRA may still be processing your original return.

### Can I amend multiple years at once?

Yes. You can submit amendment requests for multiple tax years, but each year is a separate request.

### Do I need to submit receipts when amending online?

Not always, but the CRA may contact you for supporting documents. It is best to have them ready.

### What if the CRA rejects my amendment?

If the CRA does not accept your amendment, they will explain why in a letter. You can then file a Notice of Objection if you disagree.

## Conclusion

Filing a tax amendment in Canada is straightforward, and the CRA makes it accessible both online and by mail. Whether you missed a deduction, received a late slip, or simply made an error, you have the right to correct it.

The fastest and easiest way to amend your return is through CRA My Account, where changes are typically processed within two weeks. If the amendment results in a refund, you will receive it after processing.

If you are unsure whether an amendment is needed or how to complete it correctly, a tax professional can review your situation and handle the process on your behalf.

## Get Professional Help to Maximize Your Tax Refund

Getting the right tax refund starts with an accurate return and a careful review of eligible deductions and credits. Missing a deduction or making an incorrect claim can affect your final tax outcome.

Taxccount Canada helps individuals, families, employees, students, and self-employed professionals with Canadian tax return filing and [tax planning](https://taxccount.com/tax-planning/)
. Our team can review your income, identify eligible tax-saving opportunities, and help you file accurately.

Contact Taxccount Canada to book a free consultation and get professional support with your tax return.

## Talk to a Taxccount expert

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This is general information only and not professional advice. Consult a professional before acting.

##### Written and fact-checked by [Udit Gupta](https://taxccount.com/author-bio/)

***Ex Big4, Ernst & Young, Deloitte | International & Cross-Border Tax Specialist | CPA Canada In Depth Tax Training | Licensed Chartered Accountant from ICAI & MIA***

Udit Gupta has over 15 years of experience helping corporations & business owners with corporate structuring, corporate tax filing, bookkeeping, payroll, GST/HST, cross-border tax and CRA representation. Big 4 trained at Ernst & Young and Deloitte, and qualified as a Chartered Accountant in India and Malaysia, he founded accounting firm in 2014 to serve entrepreneurs, startups and non-resident business owners across Canada. [View Full Member Bio.](https://taxccount.com/author-bio/)

**Indian Institute of Chartered Accountant Member No. (521458) | Malaysian Institute of Accountants Membership number (CA 44667) | Ex Big4,Ex Ernst & Young (EY), Ex-Deloitte | CPA Canada In-Depth Tax Training 19 Dec 2023, 12 Jul 2022, 5 Jul 2023**  
**Editorial policy. Every article is researched against primary sources — the Income Tax Act, CRA publications and CPA Canada.**

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