Notice of reassessment: why the CRA changed your return and what to do

Notice of reassessment meaning

A notice of reassessment is the CRA's revised result for a tax year it has already assessed. The first result is the notice of assessment; any later change, in either direction, produces a reassessment. The CRA only sends one when something on the assessed return actually changes.

The NOR uses the same layout as the original notice: notice details, account summary, the key line amounts and an explanation section. The difference is that the figures now reflect the change, and the explanation says what was altered and why. From that point the NOR, not the original NOA, is the current result for that year.

Why did I get a notice of reassessment from the CRA?

Reassessments come from two directions: you asked for a change, or the CRA looked at the return again. The explanation section tells you which.

You asked for the change

If you added a missed slip, claimed a forgotten credit or fixed an error through Change my return, ReFILE or Form T1-ADJ, the NOR is the CRA's answer. If it did not accept the request, you get a letter explaining why instead.

The CRA reviewed the return

Several CRA review programs work after the notice of assessment is issued. The ones people meet most often are:

• Processing Review Program: checks claims after assessment and asks for receipts, for example for medical expenses, charitable donations or childcare.
• Matching Program: compares your return with slips from employers and financial institutions and adds income you did not report.
• Request Verification Program: checks a change you asked for before issuing the reassessment.
• Refund Examination and Supplementary Examination: look at refund claims and income or deduction amounts in more detail.

A reassessment after a review is not an audit. If you did not reply to a review letter in time, the CRA may simply have removed the claim it was checking. The CRA review letter page explains how those letters work.

Reading the explanation of changes

Start with the explanation section, not the account summary. It names the line that changed, the old and new amounts in most cases, and the reason. Then compare the key lines in the summary with your own return and with the original notice of assessment.

Here is a worked example. Your 2025 NOA showed a nil balance. Months later, the Matching Program finds a T4A slip with $2,400 in box 20 self-employed commissions that was not on your return. The NOR adds $2,400 to income; if that income falls in the 14.5% federal rate for 2025 plus a provincial rate, the extra tax is several hundred dollars, and interest runs on it from the original balance-due date. The NOR shows the new Amount due.

Notice of reassessment refund or balance owing

The account summary on a reassessment works like the original: Refund, Amount due or Balance: Nil. What it shows is the result after the change, which may include amounts carried over from earlier assessments.

If the CRA owes you money because of a reassessment, it may pay compound daily interest in some cases. The interest starts on the latest of 30 days after the balance-due date, 30 days after you filed, or the day you overpaid. The rate on overpayments to individuals was 5% for July to September 2026 and is reset every quarter.

CRA reassessment dispute: if you disagree

First decide which problem you have. If you left something out or can now send the receipt the CRA wanted, you do not need a dispute. The CRA accepts new documents after a review and will look at the claim again, or you can file a change request.

If your information was complete and you believe the CRA misread the facts or applied the law wrongly, file a formal notice of objection.

Notice of objection to the CRA: deadline and methods

For individuals, the deadline is the later of one year after the filing deadline for that return (April 30, or June 15 for self-employed filers) and 90 days after the date on the notice of reassessment. For a 2025 return reassessed on October 1, 2026, that means the later of April 30, 2027 and December 30, 2026, so April 30, 2027.

1. Read the explanation of changes and gather the documents that support your position.
2. File the objection online through your CRA account, on Form T400A, or by a signed letter to the Chief of Appeals.
3. State the facts and the reasons you disagree for each issue.
4. Keep all records until the objection is resolved and any further appeal period has passed.
5. If you missed the deadline, you can apply for an extension up to one year after it.