How to Change Your Personal Tax Return After It Has Been Filed

Despite your best efforts (and/or your accountants’), occasional errors or omissions relating to your personal tax return are unavoidable.  It is possible that you forgot to include a tax slip, overstated your expenses or was unaware of a specific tax credit.  Luckily there is fairly simple mechanism that allows you to change your tax return, which can be done online or by filling out a form and mailing it in.


Examples where an amended return might be required: 

  • You forgot to include a tax slip e.g. A T4A or a T5.  Often this is caught by the revenue agencies, so it is important to wait for your notice of assessment before filing an amendment.
  • If you are a small business owner, you may have omitted or misstated some revenues or expenses or your calculations for home office or car expenses may be incorrect.
  • You might only realize after you have submitted your tax return that you are entitled to a tax credit eg. the new home buyer’s credit or the hybrid car tax credit.
  • Your RRSP contributions are incorrect or missing.
  • Education or tuition tax credits have not been included. 

In some cases Revenue Canada (or Quebec)  will make the adjustment automatically based on information that they already have (e.g. data from T4 and T5 slips) and will reflect it on your assessment (which you should always keep if only to make your accountant happy).    When the assessment does not reflect the specific error or omission, you can then go ahead initiate the process for changing your tax return.

How to file an amended return:

Revenue Canada recommends that you should wait to receive your notice of assessment before filing an amended return.  If the error or omission has not been reflected on the assessment then you should proceed to submit the amendment.  Luckily, you are not required to redo your entire return;, rather you just need to submit details regarding the specific changes.


Revenue Canada allows you to submit changes electronically.  This process can be initiated on the “your account” section of their website which actually gives you access to all of your personal tax information and is certainly worth signing up for.  You will need the following information to register:

  • your social insurance number;
  • your date of birth;
  • your current postal code or ZIP code and;
  • an amount you entered on your income tax and benefit return, so have your copy on hand (the line requested will vary and it could be from either the current tax year or the previous one).

Once you have registered and logged in, the option to change your return can be found on the left hand side under “tax returns”  Select this option and follow the steps.  Keep in mind that there are certain restrictions which can be found here.  You are also only allowed to change your return for the current and prior two taxation years.

By Mail via T1 Adjustment form

If you don’t have access to the online service or you would rather just submit the changes manually, you can either fill out the T1 Adjustment Request or you can also actually just submit a letter providing details of the change along with your personal and contact details.  You should also submit supporting documentation at this time to avoid a complicated back and forth.  Keep in mind that it takes significantly longer to process a request received via mail then online.  Once the change is processed you will receive a notice of reassessment and details on whether the amendment was accepted.

Amend/Change a return with Revenue Quebec

The process for changing or amending your return is essentially the same with Revenue Quebec.  You can either do it online or you can fill out the Request for an Adjustment to an Income Tax Return jfa;l;ka    (form TP-1.R-V).

For details on how to change the return with Revenue Quebec you can refer to “changing a return that is already filed

Use your Tax Software to Change Your Tax Return

If you used tax software to prepare the return for which you are requesting an amendment, you can usually access the adjustment form there.  It will prompt you for the details after which you will need just need to print and sign the form.

If you are using UFile to prepare your tax return, the form can be created at the interview setup where you would select “Adjustment request for a tax return that has already been filed”.  Scroll down to “Adjustment Request “to locate the data section for both Revenue Canada and Revenue Quebec

Voluntary Disclosure Program

Any adjustments that result in an increase in your taxes payable could lead to penalties, which, depending on the amounts and the time period that has elapsed, can be significant.  To encourage taxpayers to come forward with any potential omissions or errors that result in higher taxes, the CRA and Revenue Quebec have a voluntary disclosure program which, if certain conditions are adhered to, may waive these penalties and potential prosecution.  Details can be found at the links below:

Revenue Canada Voluntary Disclosure Program

Revenue Quebec Voluntary Disclosure Program

Amending your tax return is actually fairly straightforward and despite the overwhelming urge to procrastinate (it is bad enough that you have to do your taxes once a year), it is best to get it done as soon as possible after you have discovered the error (and received your notice of assessment) to avoid having the revenue agency discover it thereby creating problems, penalties and potential prosecution.