T1 adjustment request

When you can ask and what you can change

Your notice of assessment has to arrive first, and the return must be one that you or your tax preparer filed. If a request is already with the CRA, wait for its answer before sending another. A request can add income (a T4 slip or tips, for instance), claim a deduction, credit or expense you missed, or supply a slip you left out, such as an RRSP contribution receipt.

It is not the route for applying for a benefit or credit, making or changing an election, moving a refund to another CRA account, or updating personal details such as your address, direct deposit, marital status or name. Those go through other channels.

Three ways to submit it

Change my return, in your CRA account, is the online option, and the CRA gives a processing time of within two weeks. ReFILE is available in certified tax software when the original return was filed with it. By mail, you complete Form T1-ADJ with your SIN, tax year, authorization details, revised amounts and daytime phone number, and attach supporting documents for the entire amount, including amounts you claimed earlier without sending documents. Mail takes within 19 weeks of receipt.

Send a paper request separately from your current-year return. Some requests can take up to 35 weeks, such as those covering multiple returns, years beyond the normal three-year reassessment period, a loss carryback, an elected split-pension amount or a CRA request for more documents. Returns for 2015 or earlier go by mail, and a refund cannot be issued for a request made more than 10 calendar years after the end of the tax year.

An illustrative example

Suppose, for illustration, your 2025 return was assessed and you later find a $2,000 RRSP contribution receipt you did not enter. You keep the receipt and add it through Change my return. The refund depends on your income and rates. If the CRA accepts the change, it issues a notice of reassessment showing the new result.

What happens after you submit

The CRA describes three outcomes. If the adjustments are complete, you get a notice of reassessment. If only some are made, you get a notice plus an explanation of what was not changed. If none are made, a letter explains why. Replies arrive in online mail unless you chose letter mail.

Save the confirmation number from an online request, and compare the notice with what you asked for. Our entries on reassessment and notice of objection cover how long the CRA has to reassess and what to do if you disagree with its decision. If you are correcting an older error or omission, the Voluntary Disclosures Program is another option to raise with your accountant.

What to discuss with your accountant

Bring the notice of assessment, the original return, the new slip or receipt. Ask whether the change is worth requesting now, whether it affects other years or benefits, and which submission options are open for your year and situation. If your accountant files for you, confirm they have at least level 2 access.