How to Amend Your Tax Return with the CRA

Why Amend Your Tax Return?

There are many legitimate reasons to amend a tax return. The most common is discovering that you missed a deduction or credit that you were entitled to claim. Other reasons include receiving a corrected tax slip after filing (such as an amended T4 or T5), needing to report additional income you forgot about, correcting personal information, or changing how you allocated income or deductions between spouses.

The CRA estimates that millions of Canadians overpay their taxes each year simply because they do not claim all available deductions and credits. Common examples include work-from-home expenses, medical expenses, charitable donations, tuition carryforward amounts, and employment expenses. If you filed and later realize you missed something, an amendment lets you recover that money.

There is no penalty for amending your return to claim additional deductions or credits that you legitimately qualify for. The CRA may even owe you interest on the refund from the date of your original filing. However, if you are amending to report additional income you failed to include, interest and penalties may apply on the additional tax owing.

The 10-Year Adjustment Window

Under Canadian tax law, you can request an adjustment to any return filed within the last 10 calendar years. For example, in 2026, you can amend returns from 2016 through 2025. This means that even deductions missed years ago can still be claimed.

The 10-year window applies to most types of changes, including claiming deductions you missed, adding credits, changing your filing status, and correcting reported amounts. Some specific provisions, such as the capital gains reserve or loss carrybacks, have their own time limits, but the general adjustment window is generous.

It is worth noting that the CRA can also reassess your return within this period, so accuracy matters both ways. If you discover that you have been overclaiming something, it is better to voluntarily correct it through the Voluntary Disclosures Program than to wait for the CRA to find it during an audit.

Method 1: ReFILE (Online)

ReFILE is the fastest and most convenient way to amend your return. It is available through CRA-certified tax software and through CRA My Account. You can use ReFILE for returns from the 2020 tax year onward (as of 2026).

Step-by-Step Process

1. Log in to CRA My Account at canada.ca/my-cra-account using your credentials. If you do not have an account, you can register with your SIN, date of birth, and a previous return.
2. Navigate to "Change my return" under the Tax Returns section. Select the tax year you want to amend.
3. Select the line(s) to change. You will see a list of lines from your original return. Select each line where you want to make a change.
4. Enter the corrected amounts. For each selected line, enter the new amount. The system will calculate the difference and show you the expected impact on your assessment.
5. Provide an explanation.For each change, you must briefly explain why you are making the adjustment. Be specific: "Forgot to claim work-from-home expenses using detailed method, T2200 attached" is better than "missed deduction."
6. Submit. Review your changes and submit. You will receive a confirmation number. Keep this for your records.

Processing time: ReFILE adjustments are typically processed within 2 weeks, though it can take up to 8 weeks during peak periods (March through June). Simple changes involving a single line are usually faster.

Method 2: T1 Adjustment Request (T1-ADJ)

If you cannot use ReFILE (for example, because you are amending a return from before 2020, or because you need to make a change that ReFILE does not support), you can submit a paper T1 Adjustment Request.

Step-by-Step Process

1. Download form T1-ADJ from the CRA website at canada.ca. You can also call the CRA at 1-800-959-8281 to request a paper copy by mail.
2. Complete Part 1 with your identification information: full name, SIN, address, date of birth, and the tax year you want to change.
3. Complete Part 2 by listing each line number you want to change, the original amount, the revised amount, and the difference. Be precise with line numbers as they appear on the T1 General.
4. Complete Part 3 with a detailed explanation of each change. The CRA recommends being as specific as possible. Include references to any supporting documents.
5. Attach supporting documents. Include any receipts, tax slips, T2200 forms, or other documentation that supports your changes. Send copies, not originals.
6. Mail to your tax centre. Find your designated tax centre based on your province of residence. The addresses are listed on the T1-ADJ form and on the CRA website.

Processing time: Paper adjustments take 8 to 12 weeks to process. During peak tax season, it may take longer. You can check the status of your adjustment online through CRA My Account.

ReFILE vs. T1-ADJ: Which Should You Use?

In general, use ReFILE whenever possible. It is faster, easier, and you get immediate confirmation. Use T1-ADJ when you need to amend a return older than the ReFILE cutoff, when you need to attach supporting documentation, or when the CRA requires a specific form (such as for a late-filed T2200).

Common Reasons Canadians Amend Their Returns

Based on CRA data and tax industry reports, these are the most frequent reasons for T1 adjustment requests:

• Missed work-from-home deduction: Many taxpayers were unsure about eligibility or did not know about the detailed method option.
• Forgot to claim medical expenses: Especially dental work, therapy, or prescriptions paid out of pocket that were not covered by insurance.
• Did not claim tuition carryforward: Former students who did not use their full tuition credits while in school and forgot about the carryforward.
• Missed RRSP deduction optimization: Making a contribution but not deducting it, or deducting it in the wrong year.
• Incorrect charitable donation claims: Not combining donations between spouses, or not carrying forward to exceed the $200 threshold.
• Did not claim moving expenses: Especially common for new graduates who moved for their first job.
• Missing child care expenses: Payments to babysitters or relatives that were not claimed.
• Late tax slips: Receiving a T4A, T5, or T3 after filing, either requiring additional income reporting or an additional credit.

What to Expect After Submitting

After the CRA processes your adjustment request, you will receive a Notice of Reassessment by mail. This document shows the original assessment, the changes made, and the revised balance. If the adjustment results in a refund, it will be deposited via direct deposit (if set up) or mailed as a cheque.

If the CRA disagrees with your adjustment request, they may contact you for additional documentation or deny the request entirely. You have the right to object to their decision within 90 days of the reassessment date by filing a formal Notice of Objection.

For refunds, the CRA generally pays compound daily interest from the later of the filing deadline for the original return or the date you actually filed it. This means that amendments for older tax years can include significant interest payments on top of the refund itself.

Tips for a Smooth Amendment Process

1. Wait for your NOA first. Do not submit an adjustment request until you have received your original Notice of Assessment. The CRA cannot process an adjustment while your original return is still being assessed.
2. One request at a time. If you are amending multiple tax years, submit them one at a time and wait for each to be processed before sending the next. Submitting multiple requests simultaneously can cause delays and confusion.
3. Keep copies of everything. Before submitting, make copies of all documents you are sending. If using ReFILE, take screenshots of your submission and confirmation number.
4. Be specific in your explanation.Vague explanations like "claiming more deductions" may trigger additional review. Specific explanations like "claiming medical expenses for dental work totalling $3,200 as shown on attached receipts" are processed more quickly.
5. Track your status. Log in to CRA My Account periodically to check the status of your request. If it has been more than 12 weeks with no update, call the CRA.

How MaxMyRefund Helps

Reviewing your own return for missed deductions and credits means knowing all 400+ possible claims and checking each one against your situation. MaxMyRefund automates this process. Upload your completed tax return (PDF), and our system identifies deductions and credits you may have missed, along with step-by-step instructions on how to amend.

We can check returns from the last 10 years, so even if you filed correctly this year, older returns may have missed opportunities worth recovering.