Changing your return, and disputing an assessment

After you file, the CRA sends a notice of assessment. If you then spot a mistake or something you forgot to claim, you ask the CRA to change the return. If the CRA changed something and you think it got it wrong, you can file a formal objection. The two routes are different, and picking the right one saves time.

Your notice of assessment

The notice of assessment is the CRA’s summary of your return as it processed it. If the CRA later changes an assessed return, it sends a notice of reassessment showing the changes.

You’ll find it in your CRA account once your return is processed, usually right away. The CRA sends it as online mail (with an email alert if you’ve given it your email address) unless you’ve chosen letter mail or never provided an email address.

What to check:

• Account summary: “Refund”, “Amount due” or “Balance: Nil”.
• Assessment summary: the main amounts the CRA used. Compare them with what you entered to see whether anything was changed.
• Explanation of changes: if the CRA corrected your return, it says what and why.
• Plan statements: where they apply, your RRSP deduction limit, Home Buyers’ Plan or Lifelong Learning Plan repayments, and FHSA participation room for next year.

Keep it. It also has the access code you can use to file online next year.

Fixing a mistake: ask for a change

You can ask the CRA to change a return to report income you left out (a T4 slip or tips, say), claim a deduction or credit you missed (such as child care or medical expenses), or add a missing slip like an RRSP contribution receipt.

Two timing rules:

• Wait for your notice of assessment before asking for a change.
• One request at a time. If you’ve already asked for a change, wait for the CRA’s answer before asking for another.

A change request can’t be used to apply for benefits or credits, make or revise an election (pension splitting is an exception that Change my return accepts; see below), or move a refund to another CRA account. It also can’t update your personal details, such as your address, direct deposit, marital status or name. Update those with the CRA separately.

Three ways to ask

Change my return, in your CRA account. Sign in, go to Tax returns, choose Change my return, pick the year and follow the steps. Keep the confirmation number and summary of changes. It works for most situations, and it can also apply loss carry-backs, make an election to split pension income with your spouse or common-law partner (the CRA processes a change to the split only if both of you ask for it), or claim the disability tax credit once it’s been approved.

ReFILE, in certified tax software. If you filed with certified software, look for the ReFILE option. It doesn’t have to be the same software you filed with.

Form T1-ADJ, by mail. Fill in the form with the year and the changes, attach supporting documents for the whole amount (including amounts you claimed before without sending proof), and mail it to your tax centre. Send it separately from your current year’s return.

The CRA says online requests are processed within two weeks and mailed ones within 19 weeks. Some take up to 35 weeks, including changes covering several returns, years past the normal three-year reassessment period, loss carry-backs, pension splitting, and requests where the CRA has to ask you for more information. Any refund is sent as soon as the request is processed.

How far back you can go

• Change my return covers the 10 previous calendar years. A request made in 2026 can change returns for 2016 or later.
• ReFILE covers only recent years. The CRA’s tax software pages list 2022 to 2025 for the season that runs until January 29, 2027. For an older year, use Change my return or mail.
• Older years can be changed by mail, but the CRA can’t issue a refund for a change requested more than 10 calendar years after the end of the tax year.

Some returns can be changed only by mail, such as a bankruptcy return, an optional return for someone who died, or a return filed with the wrong province or territory.

Mistakes to avoid

• Don’t file a second return for the same year to fix one you’ve already sent. Wait for your notice of assessment, then ask for a change.
• Don’t put a T1-ADJ in the same envelope as this year’s return.
• Don’t file an objection just to add something you forgot. A change request is the route for that, and the CRA notes it may be faster to let a pending change request finish than to object.

For common errors to avoid in the first place, see common tax-return mistakes.

If you disagree: file an objection

An objection is for when you think the CRA misinterpreted the facts or applied the tax law incorrectly in a notice of assessment or reassessment, or in a notice about your benefits or credits.

Deadline. For individuals, it’s whichever is later:

• one year after the filing deadline for that return, or
• 90 days after the date on the notice.

If the dispute is about TFSA or RRSP contributions, the deadline is 90 days from the notice. If you missed the deadline because you were trying to sort it out with the CRA, or because of circumstances beyond your control, you can ask for an extension up to one year after the deadline.

How. Online, choose “Register my formal dispute” in your CRA account; you’ll get a case number to use when you send documents. Or mail Form T400A, or a signed letter, to the Chief of Appeals at the Appeals Intake Centre. Explain what you disagree with and why, and include the facts and supporting documents.

Paying while you wait. In most cases you don’t have to pay disputed income tax until the CRA finishes reviewing your objection. But interest keeps adding up on any amount owing while it’s in dispute, so paying some or all of it limits the interest.

If you disagree with the CRA’s decision on your objection, you can appeal to the Tax Court of Canada.

Quebec residents

Your Quebec provincial return is filed separately, with Revenu Québec. The CRA services described here are for your federal return. For your Quebec return, contact Revenu Québec.

In short

• Read your notice of assessment as soon as it arrives.
• Missed something? Wait for the notice, then use Change my return or ReFILE (or Form T1-ADJ by mail).
• Think the CRA got it wrong? Object by the deadline, and consider paying to limit interest.