How to amend your 2025 tax return
If you filed your 2025 T1 return and later discovered a mistake or missing slip, you can request an adjustment. Do not file a new return — use one of the three methods below.
On this page
When to amend
Amend your return if: you received a T3 or T5008 after filing, you forgot an RRSP deduction, you missed a credit you were eligible for, you made a calculation error, or you want to dispute a CRA reassessment by providing additional information.
Do not amend solely to change an election you already made (such as the timing of an RRSP deduction or pension income splitting) — CRA has specific rules about revoking elections that differ from ordinary amendments. Contact CRA if you need to change an election.
ReFILE — the fastest method
ReFILE is available for 2022–2025 T1 returns through any NETFILE-certified software. Open your 2025 return in the same software you originally used, make the correction, and submit via ReFILE. CRA typically processes ReFILE amendments within 2 weeks.
ReFILE is the recommended path for most amendments — it requires no forms, no mailing, and produces the fastest result. Most NETFILE software products label this clearly as "Adjust my return" or "ReFILE."
T1-ADJ via CRA My Account
Log in to CRA My Account and navigate to "Change my return" to submit an online T1 Adjustment Request. You specify the line number you want changed and the new amount. CRA processes these in approximately 4–8 weeks.
This method works well if your software doesn't support ReFILE or if you're amending a prior year return on software you no longer have installed.
Paper T1-ADJ form
Download and complete Form T1-ADJ (T1 Adjustment Request) from the CRA website and mail it to your regional tax centre. Include supporting documents (slips, receipts) that support the change. Paper processing takes 12+ weeks — significantly longer during the peak filing season from February through June.
Use paper only if you cannot access CRA My Account and your software does not support ReFILE.
Timelines and limits
The normal reassessment period is 3 years from the date of your Notice of Assessment. Within this window, you can request amendments and CRA can reassess proactively. Most amendments are processed within this period.
For amendments beyond 3 years — up to 10 years back — you can apply under the Taxpayer Relief Provisions by submitting Form RC4288. CRA has discretion on whether to accept older adjustments; genuine errors and overlooked credits are typically approved.
If an amendment results in a larger refund, CRA pays interest on the overpayment from the later of the original filing date or the payment date. If it results in more tax owing, interest runs from the original due date (April 30, 2026) — not from the amendment date.
Common mistakes
Mistake
Filing a completely new T1 return instead of an amendment
CRA will reject or ignore a duplicate T1 return. Use T1-ADJ or ReFILE to request changes to a specific filed return — never submit a second T1 for the same year.
Mistake
Amending before receiving your Notice of Assessment
Wait until CRA has processed your original return and issued a Notice of Assessment (NOA). Amending before the NOA can cause processing delays and confusion.
Quick wins
Quick win
Use ReFILE inside your original software
ReFILE is the fastest method and requires no new forms. Open your 2025 return in the same software you filed with, make the change, and submit. Most software supports ReFILE in the same workflow as original filing.
Quick win
Most common amendment: RRSP first-60-days contributions
If you contributed to an RRSP between January 1 and March 1, 2026 and forgot to claim it on your 2025 return, that's the most common amendment. ReFILE immediately — the deduction is worth recovering.
FAQ's
How long does CRA take to process an amendment?
ReFILE (electronic amendment) typically takes 2 weeks. A T1-ADJ submitted through CRA My Account takes approximately 4–8 weeks. A paper T1-ADJ mailed to your tax centre can take 12+ weeks, especially during peak filing season. CRA sends a Notice of Reassessment once the amendment is processed — this replaces your original Notice of Assessment for that year.Can I amend a return from 5 years ago?
Generally, the normal 3-year reassessment period applies to both CRA and the taxpayer — meaning you can request adjustments to returns assessed within the last 3 years. For older returns (up to 10 years back), you can still request adjustments under the Taxpayer Relief Provisions (formerly Fairness Provisions) by submitting Form RC4288. Common reasons include unclaimed credits or overlooked deductions. CRA has discretion on whether to accept adjustments beyond the 3-year window.Will amending trigger an audit?
Amending a return does not automatically trigger an audit. CRA reviews a statistical sample of returns each year, selected on risk factors — amendments are one of many signals CRA weighs. If your amendment significantly changes your return (large additional deduction, change in income), CRA may request supporting documents. Filing an amendment to correct a genuine error — especially one that increases your taxes — is always the right move and demonstrates good faith.What if my amendment creates a larger balance owing?
Pay the additional amount as quickly as possible. CRA will charge daily-compounding interest from the original due date (April 30, 2026 for the 2025 return) on any additional balance revealed by an amendment — not from the amendment date. There is no late-filing penalty for amendments, only interest on the underpaid amount. The sooner you pay, the less interest accrues.