How to Amend Your Tax Return in Canada: T1 Adjustment Guide (2026)

You filed your taxes and then realized something was wrong. Maybe you forgot to claim a deduction. Maybe a new slip arrived after you submitted. Maybe you entered a number incorrectly and only noticed when you reviewed your Notice of Assessment.

Whatever happened — do not file a second tax return. That is one of the most common mistakes Canadians make, and it creates more problems than it solves. There is a proper process for this, it is straightforward, and in most cases you can complete it entirely online in under 15 minutes.

Quick Answer: To amend a Canadian tax return, use the "Change my return" service in CRA My Account (fastest — processed in about 2 weeks), the ReFILE service through your tax software, or mail Form T1-ADJ to the CRA (takes about 8 weeks). Wait until you receive your Notice of Assessment before submitting any amendment. You can go back up to 10 years.

The Golden Rule: Wait for Your NOA First

Before you do anything, wait for your Notice of Assessment (NOA). The CRA must fully process your original return before they can process any changes to it. If you submit an amendment before your NOA arrives, the CRA will simply set it aside until the original is assessed — which slows everything down.

Once your NOA is in your CRA My Account (or arrives by mail), you are clear to proceed.

3 Ways to Amend Your Canadian Tax Return in 2026

In 2026, you have three options. Here is how they compare:

For the vast majority of Canadians, "Change my return" through CRA My Account is the right choice. It is the fastest, does not require uploading receipts upfront (the CRA will ask if they need them), and gives you a confirmation number immediately.

Method 1 — "Change My Return" in CRA My Account (Step by Step)

1. Go to canada.ca/my-cra-account and sign in
2. From the main menu, select "Tax returns"
3. Select "Change my return"
4. Choose the tax year you want to amend from the list of available years
5. The tool will show your return with the original amounts. Find the line number you need to change (more on this below)
6. Enter the new amount for that line — not the difference, the new total
7. Add a brief explanation of why you are making the change
8. Review the summary of changes and click Submit
9. Save your confirmation number — this proves you submitted the amendment

You do not need to upload receipts when submitting online. The CRA may contact you later to verify specific claims — if they do, you will receive a message in your CRA My Account or by mail. Keep all supporting documents accessible for at least 6 years.

Which Line Numbers to Use

If you are not sure which line to change, here are the most commonly amended lines:

Method 2 — ReFILE Through Your Tax Software

If you originally filed using NETFILE-certified tax software (TurboTax, Wealthsimple Tax, UFile, H&R Block, etc.), you can use ReFILE to submit your amendment directly through that same software without going to CRA My Account.

How ReFILE Works

1. Open your tax software and load your filed return for the year you want to amend
2. Make the necessary changes to the return
3. The software will detect the differences between the original filed version and your new version
4. It generates an amendment summary showing what changed
5. You transmit the amendment through ReFILE — just like you submitted the original via NETFILE
6. You receive an immediate acceptance or rejection confirmation from the CRA

ReFILE is available for tax years 2021 through 2026 returns filed in 2026. Returns filed for years before 2021 must be amended using "Change my return" or Form T1-ADJ by mail.

When You Cannot Use ReFILE

• If a CRA assessment or reassessment is already in progress on that return
• If you need to change information on page 1 of your T1 (name, SIN, address, province)
• If the original return was filed on paper — ReFILE requires the original to have been submitted via NETFILE
• If the return is for a non-resident, emigrant, deceased person, or bankrupt individual

If ReFILE is unavailable for your situation, use "Change my return" in CRA My Account or mail a T1-ADJ.

Method 3 — Form T1-ADJ by Mail

Some returns can only be amended by mail — particularly non-resident returns, returns filed in the wrong province, and a few other special situations. For everyone else, mail is simply the slowest option.

How to Complete and Mail Form T1-ADJ

1. Download Form T1-ADJ (T1 Adjustment Request) from canada.ca
2. Fill in your name, SIN, address, and the tax year being amended
3. In Area C (the changes section), list each line number you are changing, the original amount (from your NOA), and the new amount you are requesting
4. Write a brief explanation for each change
5. Attach all supporting documents — including receipts for claims you already had on the return, not just the new ones
6. Sign and date the form
7. Mail to the CRA tax centre for your province (address listed on the back of the form)

Important mail tip: Send your T1-ADJ separately from any other CRA correspondence. Do not mail it in the same envelope as your current year's return. Use tracked mail so you can confirm delivery.

What Happens After You Submit

Once you submit your amendment — by any method — the CRA reviews the changes and responds in one of two ways:

• Notice of Reassessment (NOR): The CRA accepted your changes (fully or partially) and has updated your return. The NOR shows the revised result — including any additional refund owing to you or updated balance.
• Letter of explanation: The CRA reviewed your request but did not make the changes you asked for, and is explaining why. This is not a final decision — you can provide additional documentation or file a formal objection if you disagree.

Will You Get a Bigger Refund?

If your amendment results in a lower tax owing than originally calculated, the CRA will issue the difference as a refund — to your direct deposit account if it is set up, or by cheque. The refund is issued after the reassessment is complete, typically within 2 weeks of a successful online amendment.

What If You Owe More After the Amendment?

If your amendment results in additional tax owing — for example, because you are adding income you missed — the new balance is due immediately. Interest applies from the original April 30 deadline, not from the date of your amendment. Pay the new balance as quickly as possible to stop further interest from accruing.

What You Can and Cannot Change Online

Most amendments can be made through "Change my return" in CRA My Account. However, some situations require a paper T1-ADJ:

How Far Back Can You Amend?

In 2026, you can request changes to a return from any of the previous 10 tax years — going back to the 2016 tax year. However, there is an important nuance:

• Refunds: The CRA can only issue a refund for an amendment if the request is made within 10 years of the end of the tax year. For 2026, this means amendments requesting refunds for the 2016 tax year must be submitted before December 31, 2026.
• Additional taxes owing: If your amendment results in more tax owing, the CRA can also reassess going back further in cases of misrepresentation or fraud — typically up to the normal reassessment period of 3 years from your NOA, extended to 6 years if misrepresentation is suspected.

If you have been missing deductions for years — unclaimed RRSP contributions, medical expenses you never submitted, charitable donations you forgot to include — a review of past returns going back to 2016 may be worth the time. Recovered refunds from multiple years can add up significantly.

Quebec Residents: You Also Need to Amend Your Provincial Return

If you live in Quebec, remember that you file two separate returns — a federal T1 with the CRA and a provincial TP-1 with Revenu Québec. Amending one does not automatically amend the other.

If your amendment affects your provincial return (which most income and deduction changes do), you must also amend your TP-1 through Revenu Québec's My Account for citizens (Mon dossier) or by submitting their provincial amendment form. The two amendments are independent processes with separate timelines.

Common Mistakes to Avoid

• Filing a second tax return for the same year. Do not do this. The CRA processes one T1 per taxpayer per year. Filing a second return creates a processing conflict and significant delays.
• Submitting before your NOA arrives. The amendment will be held until the original is assessed. Always wait for the NOA.
• Not keeping copies of what you submitted. Save your confirmation number for online amendments, or use tracked mail for paper submissions.
• Forgetting to include receipts for existing claims (mail method). When mailing a T1-ADJ, you must include supporting documents for all claims on the lines you are changing — not just the new ones. The CRA needs to verify the full amount, not just the change.
• Making changes while an assessment is already in progress. If the CRA is currently reviewing your return, wait until that process is complete before submitting an amendment.

Frequently Asked Questions

How do I amend my tax return in Canada?

The fastest way is through CRA My Account using the "Change my return" service — processed in about 2 weeks. You can also use ReFILE through NETFILE-certified tax software if you originally filed electronically. For returns that cannot be changed online, mail Form T1-ADJ to your CRA tax centre. Always wait for your Notice of Assessment before submitting any amendment.

What is a T1 Adjustment?

A T1 Adjustment is the official CRA process for changing a personal income tax return that has already been filed and assessed. It is how you fix errors, add missed deductions or income, claim forgotten credits, or correct any other mistake on a previously filed T1 return. It is not the same as filing a new return — it is a specific change request applied to the existing filed return.

How long does a T1 Adjustment take?

Online amendments through CRA My Account or ReFILE are typically processed within 2 weeks. Paper T1-ADJ forms sent by mail take approximately 8 weeks. Processing times can vary during peak periods (April–June) when CRA volume is highest.

Can I amend a tax return from several years ago?

Yes. In 2026, you can amend returns going back to the 2016 tax year — a 10-year window. Amendments that result in a refund must be requested before the end of the 10th calendar year after the tax year in question. For the 2016 tax year, this deadline is December 31, 2026.

Do I need to upload receipts when amending online?

No — when using "Change my return" in CRA My Account, you do not need to upload supporting documents upfront. The CRA will contact you separately if they want to verify any claims. Keep all your receipts and records accessible for at least 6 years in case they are requested.

What happens after I submit a T1 Adjustment?

The CRA reviews your amendment and responds with either a Notice of Reassessment (the changes were accepted and your return is updated) or a letter explaining why the changes were not made. If the reassessment results in a refund, it is issued after processing. If it results in additional tax owing, the balance is due immediately — with interest from the original April 30 deadline.

I filed in the wrong province. How do I fix it?

This cannot be changed online — it must be fixed by mailing a T1-ADJ. Include all the required forms for the correct province of residence and a clear explanation of the error. The CRA will reassess your return using the correct provincial tax rates and credits.

Can I use ReFILE for any tax year?

In 2026, ReFILE is available for adjustments to the 2021, 2022, 2023, 2024, and 2026 tax years — provided the original return was filed via NETFILE. Returns from before 2021 must be amended using "Change my return" in CRA My Account or Form T1-ADJ by mail.

I owe more money after my amendment. When is it due?

The additional tax is due immediately upon reassessment. Interest applies from the original filing deadline (April 30) — not from the date you submitted the amendment. Pay the new balance as quickly as possible to minimize interest. If you cannot pay in full, contact the CRA to set up a payment arrangement.

I live in Quebec. Do I need to amend both my federal and provincial returns?

Yes. Quebec residents file separate returns with the CRA (T1) and Revenu Québec (TP-1). Amending one does not automatically amend the other. If your change affects both returns — which most income and deduction changes do — you must submit amendments separately to both the CRA and Revenu Québec through their respective online portals or by mail.

What if the CRA made an error on my return — not me?

If the CRA made an error when processing your return (shown in the "Explanation of Changes" section of your NOA), you can still use the same amendment process to correct it. If the CRA's position is incorrect and you disagree after submitting your amendment, you can file a formal Notice of Objection within 90 days of your reassessment date.

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Disclaimer: This article is for general educational purposes only and does not constitute professional tax advice. CRA procedures and available online services can change. For complex amendments or large amounts, consult a qualified Canadian tax professional before proceeding.

If you want to know other articles similar to How to Amend Your Tax Return in Canada: T1 Adjustment Guide (2026)y ou can visit the category Canadian Financial and Income Tax Calculators.