Making a mistake on your T1 General Income Tax and Benefit Return isn’t the end of the world. In fact, the Canada Revenue Agency (CRA) understands that errors can happen—from entering the wrong amount, missing a slip, forgetting a deduction, or even reporting incorrect personal information. The good news is that there’s a structured and straightforward process to correct errors after you’ve filed your return, and it’s known as the T1 Adjustment Request.
This detailed guide will walk you through when and how to amend your tax return, what forms or tools to use, how long it takes, and what to watch out for when making corrections to avoid further complications.
1. Can You Make Changes After You’ve Filed?
Yes. If you discover an error or omission after filing your T1 return, you do not need to refile the entire return. Instead, you can request a change to your original return once the CRA has processed it and issued your Notice of Assessment (NOA).
Common reasons to amend your return include:
- Forgetting to include a T4 or T5 slip
- Incorrect RRSP deduction amount
- Wrong marital status
- Omitting tuition fees or medical expenses
- Updating income or deductions after receiving late documents
2. When Can You Request a Change?
You must wait until you have received your Notice of Assessment before requesting a correction. Trying to amend your return too early will lead to your request being rejected or delayed.
Adjustments can be made for any of the 10 previous tax years. For example, in 2025, you can request changes going back to the 2015 tax year.
3. Methods to Correct Your T1 Return
You have multiple ways to request a change, depending on your comfort level and access to digital tools:
3.1 Using CRA My Account (Fastest Option)
This is the most convenient and quickest way to correct your return. Log in to CRA My Account, and choose the “Change my return” option.
- You can amend specific lines (e.g., Line 20800 for RRSPs)
- Upload documents to support your changes
- Track the status of your request online
3.2 Submitting a T1 Adjustment Request (Form T1-ADJ)
If you prefer paper filing or don’t have access to your CRA account, you can fill out Form T1-ADJ, T1 Adjustment Request. You must include:
- Details of the tax year and lines you want to change
- Explanation of why the change is needed
- Supporting documentation (slips, receipts, revised T2202, etc.)
Mail the completed form to the appropriate CRA tax centre listed on the form’s instructions. Allow 8–12 weeks for processing.
3.3 ReFILE (For Online Filers Using Certified Software)
If you filed electronically using NETFILE-certified tax software, you may be able to use the ReFILE service to submit corrections directly through the software—provided it supports the ReFILE option.
This is only available for recent returns and cannot be used if your return was filed on paper or if certain CRA review flags are present.
4. What Information Can You Correct?
You can request adjustments to most lines of your T1 return, including:
- Employment income (Line 10100)
- RRSP deductions (Line 20800)
- Tuition and education credits (Line 32300)
- Medical expenses (Line 33099)
- Charitable donations (Line 34900)
- Disability amounts (Line 31600)
You can also update your marital status, dependent information, or province of residence if it was filed incorrectly.
5. How Long Does It Take for the CRA to Process Changes?
- Online (CRA My Account or ReFILE): Usually processed within 2–3 weeks
- Mail (T1-ADJ): Can take 8–12 weeks, sometimes longer during peak periods
You can monitor the progress of your request through CRA My Account or by calling the CRA at 1-800-959-8281.
6. Supporting Documentation Requirements
You must provide adequate documentation to support your correction. Examples include:
- Missing T4, T4A, T5 slips
- Amended or reissued tuition receipts (T2202)
- Receipts for medical, childcare, or moving expenses
- Void cheques for direct deposit updates (if correcting banking info)
Never send original documents; use photocopies or scanned versions unless explicitly requested by the CRA.
7. Will Correcting Your Return Trigger a Review?
In some cases, submitting a T1 adjustment may lead the CRA to review your entire return. This doesn’t necessarily mean you’re being audited—it’s just a quality control step.
To avoid delays, ensure that your documentation clearly supports your claim and your explanations are concise and factual.
8. What Happens After the Change Is Processed?
Once the CRA processes your correction, they will send you a Notice of Reassessment. This document will show your adjusted taxable income, any changes to credits or refunds, and any new balance owing or refund due.
If the correction results in a refund, the CRA will issue it via direct deposit or cheque. If you now owe more tax, you’ll be expected to pay the balance by the due date indicated to avoid interest.
9. Can You Cancel a Requested Change?
If you realize you submitted the wrong information in your correction request, contact the CRA immediately. If your request hasn’t yet been processed, they may be able to cancel or halt the adjustment. Otherwise, you may have to submit another T1-ADJ to correct the correction.
10. Final Tips for Correcting Your T1 Return
- Wait until your original return has been assessed before requesting changes
- Use CRA My Account for faster processing and tracking
- Double-check your changes and documentation before submission
- Only request changes for specific errors—don’t resubmit the entire return
- Maintain all correspondence and documents for your records
11. Final Thoughts
Errors on tax returns are common, but the CRA provides flexible tools for making corrections. Whether you forgot a slip, omitted a deduction, or discovered new information, the T1 Adjustment process allows you to amend your return efficiently.
Use the appropriate method—online, ReFILE, or Form T1-ADJ—and ensure your documentation is complete. By taking quick action and following the proper steps, you can resolve mistakes without penalties and ensure your taxes are accurate and up to date.
When in doubt, consult with a professional tax preparer or contact the CRA for personalized guidance.
