Here's some additional information on making an amendment to your return:
You already filed your tax return, it was accepted by the CRA, and
now you received additional forms or tax information or you need to
If so, you need to amend the tax return
you already filed. First, be sure the return was accepted by the CRA,
and do not change the return you already filed. Amended returns must be
filed on a new form called T1-ADJ, T1 Adjustment Request.
Follow these steps:
Sorry but this is going to be complicated. Once you have filed a completed income tax return, you cannot & must not try to submit another "corrected" return. The system will not accept it. You have to prepare a special form called "ADJUSTMENT REQUEST". T1ADJ is the form number. TurboTax has this form in its program. Click on the "FORMS" selection box & look for the ADJUSTMENT REQUEST or T1ADJ form. If you use the T1ADJ form that is already in your previously filed return, it will open with some of the required information, such as name, address etc already entered. The detailed instructions about how to complete this form are on the second page, along with the address of your tax center. When you have completed the ADJUSTMENT REQUEST form, you MUST MAIL IT, (Yes, MAIL IT), to your tax center. Under the section C, ADJUSTMENT DETAILS, enter the line number or the schedule name that you want to change. RRSP info is on schedule 7. Enter the information needed using the column names. They are quite understandable. Under "OTHER DETAILS or EXPLANATIONS", type in something like "Please amend my 2014 tax return to include the above change to my RRSP deduction" or something along those lines. Attach copies of ALL documents needed to backup your claim. NO RECEIPTS = NO ACTION! Make copies of everything you send to CRA. Be prepared, Adjustment Requests take several months to process, especially during tax season.
Alternatively, you might try using the CRA's "My Account" online service to request a change on your return, especially if no supporting documentation needs to be included, at least initially.
Either way, it is also best to at least wait for your Notice of Assessment to arrive before doing this. Depending on the type of error, they might have corrected it too.