T1 Adjustment Form (T1-ADJ): Change a Filed Tax Return
The T1 Adjustment Request (form T1-ADJ) is how you ask the Canada Revenue Agency to change a personal income tax return you have already filed — to add a slip you missed, claim a credit you forgot, or correct an amount. The paper form is only one of three ways to do it — pick the route that fits you below.
Online in your CRA account
CRA service standard: within 2 weeks
Use the “Change my return” service inside your CRA account. The CRA lists online requests as the faster option.
How “Change my return” works (canada.ca)Through certified tax software (ReFILE)
CRA service standard: within 2 weeks
If your return was filed through certified tax software, the same software can usually send the correction electronically.
Compare the options (canada.ca)Paper form T1-ADJ by mail
CRA service standard: within 10 weeks
Download the official form, fill in the lines you're changing, attach supporting documents and mail it to your tax centre.
Download the official T1-ADJ (canada.ca)Have an accountant handle it
Several years to fix, an older year, foreign income, or a CRA letter on top — that's our daily work. Free consultation first.
Get help with a tax adjustmentOpens the current version on the Government of Canada website — always the up-to-date form, straight from the source.
When you'd use form T1-ADJ
Use a T1 adjustment when a return you already filed needs a change: you received a slip after filing (a T4, T5 or T3), you forgot a deduction or credit (medical expenses, donations, tuition), or a number was entered incorrectly.
Wait until you receive your Notice of Assessment for that year before you request a change. Asking for an adjustment before the return is assessed can cause delays or be rejected.
How to submit a T1 adjustment
There are generally three ways to change a filed return: online through your CRA account ("Change my return"), electronically through certified tax software (ReFILE), or by mailing a completed paper T1-ADJ form. The CRA lists online as the faster route — all three options are in the chooser at the top of this page.
On the paper form you enter the tax year, the line numbers you're changing, the previous and revised amounts, and a short reason for each change. Attach supporting documents (slips, receipts) for the amounts you're changing, and mail it to the tax centre that serves your area — the current mailing addresses are listed on the CRA form page linked above.
How long it takes and how far back you can go
As a service standard the CRA aims to process online change requests within about two weeks and mailed requests within about ten weeks. Times can be longer — for example when you change several years at once, an older year, or a more complex return. These are CRA estimates, not guarantees.
You can generally ask the CRA to adjust the current year and earlier years, but a refund from an adjustment generally cannot be issued more than 10 calendar years after the end of the tax year.
Common mistakes
Sending the adjustment before the Notice of Assessment arrives, forgetting to attach the supporting documents, or filing separate paper requests for several years when one online submission per year would be cleaner. The CRA also asks you to wait for a response to one change request before sending another for the same return. If you're adjusting multiple years, or you're not sure a change is worth it, it's usually worth a quick review first.
Official CRA references
FAQ
They do the same thing — ask the CRA to change an already-filed return. ReFILE sends the change electronically through certified software; the T1-ADJ is the paper version you mail in.
You can generally request a change for the current year and earlier years, but a refund from an adjustment generally cannot be issued more than 10 calendar years after the end of the tax year.
The CRA's service standard is within about two weeks online and within about ten weeks by mail. Complex cases — several years, an older year, or a return under review — can take longer. These are estimates, not guarantees.
Yes. Request the change after the return has been assessed and you've received your Notice of Assessment for that year.
Sometimes. If some years were never filed at all (not just filed with an error), that's catch-up filing rather than an adjustment, and it may fall under the CRA's Voluntary Disclosures Program. We can look at your years together and tell you what each one needs.
Fixing more than one year, or not sure where you stand?
We handle complex adjustments and catch-up filing — several years, older returns, CRA letters. Book a free consultation and we'll tell you exactly what each year needs.
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Other CRA forms
General information only, not tax advice. This is a copy of publicly available information about an official Government of Canada form; the form itself is published by the CRA. Verify details for your situation on canada.ca or with us.