Changing a Tax Return You Already Filed

A slip that turned up late, or a medical receipt that never made it onto last year's return, can still be added. Just don't do it by filing the return again.

What you can and can't change

Once a return has been assessed, you can ask the CRA to change it to report income you left off, claim a deduction, credit or expense you missed (childcare or medical costs, for example), or add a missing slip such as an RRSP contribution receipt.

A change request can't be used to apply for benefits or credits, make or revise an election, move a refund to another CRA account, or update personal details like your address, direct deposit, marital status or name. Those go through other channels.

Timing matters too. You have to wait for your notice of assessment before asking for a change, and if you already have a request in, wait for the CRA's answer before sending another one.

Don't file a second return

If you have new information for a return you've already sent, the CRA says not to file another return for that year. You ask for a change to the original instead. The exception is a year you never filed that the CRA assessed anyway. To change that one, you file a paper return for that year.

Three ways to ask

You don't have to ReFILE with the same software you first used, though the CRA notes it may be easier. Neither online option handles a bankruptcy return, an optional return for someone who died, or a return filed with the wrong province of residence. Those changes go by mail.

If you mail a T1-ADJ, send it to your tax centre on its own, not with your current-year return. Attach supporting documents for the whole amount, including anything you claimed before but never sent receipts for.

How far back you can go

As a general rule, the CRA only considers changes for tax years ending in the previous 10 calendar years. For a request made in 2026, that means 2016 or later, and Change my return won't take anything earlier. You can still mail a request for 2015 or before, but the CRA can't issue a refund for an adjustment requested more than 10 calendar years after the end of the tax year.

Some requests take longer. The CRA says changes can take up to 35 weeks when they involve things like more than one return, a year past the normal three-year reassessment period, a loss carryback, split pension amounts, or a request from the CRA for more documents.

What happens next

The CRA may review your request before reassessing, to check that the change is allowed and properly supported, so keep the receipts handy. If it makes every change, you get a notice of reassessment showing them. If it makes only some, the notice comes with an explanation of what it didn't change. If it makes none, you get a letter saying why.

The answer comes through your CRA online mail unless you've chosen letter mail or never gave the CRA an email address. Any refund goes out as soon as the request is processed.

If you disagree with the reassessment, you can file a formal objection. Our post on dealing with the CRA walks through it. For individuals the deadline is the later of one year after that return's filing deadline or 90 days after the date on the notice. If an adjustment request is still in the works, the CRA says letting it finish may be faster than objecting.

Common fixes

Two everyday examples are covered in our answers on forgotten medical expenses and a dependant you didn't claim. If the fix is income you never reported and the year is at least a year past its filing due date, the Voluntary Disclosures Program may be worth a look. Our post on catching up on back taxes explains how it works.

How we help

Fixing an earlier year's return is one of the things we help with, and that includes disability tax credit adjustments to earlier years. With your authorization we can also speak to the CRA for you and answer their letters, gathering the backup if they ask for it.