In case you find out that you need to make changes to your tax return, such as adding a deductible expense or receiving another T-slip, you can request an adjustment. However, it's best to wait until you receive your Notice of Assessment from the Canada Revenue Agency (CRA) before making any changes.
The time limit for filing adjustments by mail is ten years for most cases, except for late or amended pension splitting elections which have a limit of three years. You can request changes to your most recent return or for up to the previous 9 tax years, either online or by mail.
As of 2020, changes can be requested for the 2010 or later taxation years. If you had a tax professional file your return, they can also file an amendment for you.
Requesting a Change Online
Making a change to your tax return online is a straightforward process that involves logging in to your account on the CRA My Account page.
You have the option to request changes for multiple tax years in one session, but each year must be done individually. There are certain changes that cannot be made through My Account.
For a list of exclusions, please refer to the CRA Change my return information link provided at the bottom. When you log into My Account, if it shows a link to your most recent assessment on the Overview page, you can select the Change my return icon in order to make a change.
For a prior year, click on Go to Tax returns details, then Click on the Status of return (Assessed or Reassessed) for the year you want to revise. Once at the assessment page, go to the bottom of the page and click on the Change this return icon.
You will be prompted for the line number that you wish to change on your tax return. If you are trying to correct a prior return because you didn't enter all your RRSP contributions, see our article RRSP Contribution Not Recorded Last Year.
You can also use the online request if you forgot to apply for the GST/HST tax credit when you filed your tax return.
ReFILE Online Filing
If you filed your return using tax preparation software, you can use the same software to change your return, using CRA's ReFILE service (see link at bottom). CRA's Certified tax software for the NETFILE program indicates what level of ReFILE service each software product provides. ReFILE can be used to file amendments for the immediately past tax year and 3 previous tax years.
Some things cannot be changed using ReFILE - see ReFILE exclusions on the CRA website. To do this in your tax software, instead of Open an existing return, you probably have to choose Change a filed return
Requesting a Change by Mail
You can obtain a form T1-Adj, T1 Adjustment Request from the CRA web site, complete it and mail it in, along with documents supporting your change request.
“Please note that the information provided in this article is of a general nature and may not be accurate for your specific situation. The information is current as of the date of posting and is not intended to provide legal advice. It's always recommended that you consult with a professional accountant and lawyer for personalized guidance and advice."