How to amend a tax return

How to Amend Your Tax Return After You Have Filed?

Made a mistake on your tax return or forgot to claim a tax credit or deduction – Don’t worry you can fix it! It is not as difficult as you might think. CRA acknowledges that the tax code is complex, and that people make mistakes or miss out on some important information. Hence CRA makes it easy for you to correct your tax return if you realize your mistake after filing your return. 

A tax return can be considered ‘incorrect’ or ‘incomplete’ for a variety of different reasons. It may involve simple things like forgetting to sign a form to significant issues like misreporting income or inaccurately calculating a deduction that can all affect the validity of a tax return. Making a mistake is not a big deal, instead it is important to rectify the situation by filing an amended tax return, where appropriate. It is recommended to contact an accounting firm as they are experts in their field before moving forward by yourself.

New Info, not a New Return!

Only one tax return is accepted by CRA per tax year. Once you have filed your tax return, you cannot file a new one. But you can amend the original by making any adjustments required. You will have to wait to receive your notice of assessment from CRA before submitting any adjustment requests. This is important for a couple of reasons. First, an early adjustment request may affect the processing time of the original return causing a delay in adjusting the tax return for any mistakes. Secondly, there is a possibility that CRA may itself adjust your original return. CRA has all your information and may adjust the credits that you missed.  

Amendments can be made for 10 previous years. CRA has three ways for you to file an adjustment request once you have received your notice of assessment

  • Use the change my return option shown in My Account at;
  • Send a completed Form T1-ADJ, T1 Adjustment Request, to your tax center; or 
  • Send a signed letter to your tax center asking for an adjustment to your return.

My Account

Changes to your return can be submitted online via the portal if you are a CRA Account holder. You have to select the “change return” option after signing into your account. Then select the respective tax year to which amendment relates to and enter line numbers and figures to correct or add information. The online adjustment process is about two weeks. Once your adjustment request has been approved and processed, you will receive a Notice of Assessment outlining the approved changes. If your adjustment request is denied, a letter of explanation is issued by CRA.

Once you submit an online adjustment request, you cannot send another until the first one has been processed. So, it is advised that if you have more than one adjustment to make, keep your information all ready at once and do it all in one shot. Multiple adjustments are allowed to be added in a single request.

Some changes cannot be done online. For more details check out CRA’s “how to change your return”.

Request by Mail – Form T1-ADJ

In case you prefer to submit your tax return adjustment request by paper, fill out Form T1ADJ- T1 Adjustment Request. You can download a PDF copy of this from the CRA’s website. Provide any reasons or details and whatever backup documentation may be relevant and mail it to your local tax center

Request Letter to Local Tax Centre 

You must send this letter with information like your name, address, phone number, and social insurance number and inform which tax year you intend to amend. You will also need to provide any supporting documents for your adjustment (receipts, slips, etc).

Processing Time

  • Within 2 weeks if requested online
  • Within 8 weeks if requested by mail

Processing time may vary from this standard time if the CRA has to contact you or an authorized representative for more information or documentation.  

With more than 11 years of experience helping Canadians file their taxes confidently and get the maximum money they deserve. If you are looking for an International Tax Accountant in Canada, then feel free to reach out to Filing Taxes at 416-479-8532. Schedule your tax preparation appointment with us and take the first step towards proper management of your finances. Our professional personal tax accountants will make sure to get you the maximum tax refund on your personal tax return.


The information provided on this page is intended to provide general information. The information does not consider your personal situation and is not intended to be used without consultation from accounting and financial professionals. Salman Rundhawa and Filing Taxes will not be held liable for any problems that arise from the usage of the information provided on this page.

Written By:
Salman Rundhawa
Salman Rundhawa is the founder of Filing Taxes. Salman provides valuable tax planning, accounting, and income tax preparation services in Toronto, Mississauga, Oakville, and Hamilton.

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