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A notice of reassessment (NOR) is the CRA’s updated calculation for a tax year it has already assessed. It shows up when something on the return changed, either because the CRA found a difference or because you asked for one. For most individuals the CRA can reassess within 3 years of the original notice, and you have 90 days to dispute it.
How is a notice of reassessment different from a notice of assessment?
A notice of assessment (NOA) is the first summary the CRA sends after it processes your return. A reassessment follows only when a return that was already assessed gets changed. The CRA says processing time is generally the same for both, and a reassessment can raise your tax, lower it or leave it where it was.
Both appear in your CRA account under Tax returns or Mail, and a paper copy goes out if you haven’t signed up for online mail. If you want the basics of the first notice, our notice of assessment guide walks through it.
Why did the CRA reassess my return?
Usually a mismatch or a request. The common causes:
- A slip arrived late or was missing from your return, such as a T5 from a bank or a T4A.
- The CRA asked for receipts to support a deduction or credit, and the proof didn’t arrive or didn’t match.
- You filed a T1 adjustment or used the change-my-return service. That produces a reassessment even when it goes your way.
- A related return changed: a spouse’s, a carried-forward amount, or your RRSP deduction limit.
- A review or audit of your income, expenses or foreign property.
Read the explanation of changes first. The CRA says that if it found errors, it sends the NOR right after the reassessment is complete.
How long can the CRA reassess a return?
For an individual, the normal reassessment period is 3 years from the date of the original notice of assessment. Mutual fund trusts and corporations that aren’t Canadian-controlled private corporations get 4 years. The Income Tax Act allows later reassessment if you made a misrepresentation through neglect, carelessness or wilful default, or if you signed a waiver within the normal period.
The clock runs in your favour too. As an individual, you can ask the CRA to reassess a year to get a refund or lower your tax up to 10 calendar years after the end of that tax year. The wording is in the Government of Canada: Income Tax Act section 152.
How do I read the boxes on the notice?
The top shows the last four digits of your SIN, the tax year and the issue date. The account summary then says Refund, Amount due, or Balance: Nil. Below that is the calculation line by line, then an explanation of changes, which is the part to read first on an NOR.
Registered plan statements come last: your RRSP deduction limit, your Home Buyers’ Plan and Lifelong Learning Plan balances, and FHSA room. A reassessment can change these too. Match every changed line to your records, and if you agree, keep the notice with the return.
What does a changed refund look like in dollars?
Take an Ontario employee earning $75,000 who filed a 2024 return on 12 April 2025 with a $6,000 child care deduction. The employer withheld $12,000, and the return showed a $1,224 refund. In September 2026 the CRA asked for receipts, didn’t get them, and reassessed. The figures below are estimates from the engine behind the site’s income tax calculator, using 2026 rates as a stand-in for the 2024 rates.
| Item | Original | Reassessed |
|---|---|---|
| Tax for the year | $10,776 | $12,705 |
| Tax withheld | $12,000 | $12,000 |
| Refund (owing) | $1,224 refund | $705 owing |
Tax went up by $1,929, and the swing from refund to balance owing is the same amount. The $705 balance carries interest from 1 May 2025. At the 7% rate for October to December 2026, compounded daily, that comes to about $51 over a full year, and the rate changes every quarter. A penalty might apply as well, depending on the facts.
How long do I have to object, and does interest keep running?
An individual has until the later of one year after the filing due date or 90 days from the date on the notice. In the example the notice is dated 15 September 2026, so the 90 days end on 14 December 2026, and the year-after-due-date rule had already passed. Assessments of RRSP over-contribution tax get only the 90 days.
File through Register my formal dispute in your CRA account, or send Form T400A to the Appeals Intake Centre. The CRA normally holds off collecting the disputed amount until 90 days after it sends its decision. Interest keeps accruing on a balance in dispute, though, and paying part of it cuts the interest. If you disagree with the decision, a Tax Court of Canada appeal must be received within 90 days of the date the decision was sent.
The Canada Revenue Agency: notices of assessment and reassessment page and the Canada Revenue Agency: resolving your dispute guide cover the steps. For each quarter’s interest rate, see the Canada Revenue Agency: prescribed interest rates.
If you can’t pay what a reassessment says you owe, ask the CRA about a payment arrangement. To see what a refund might be on a normal return, try the tax refund calculator, and read our tax assessment overview.
Where does this information come from?
The NOA and NOR differences, the 90-day dispute rule and the notice layout come from the CRA’s notices page and its objection guide; the 3-year and 4-year periods are from section 152 of the Income Tax Act, the 7% interest rate is the CRA’s rate for October to December 2026, and the refund example is an estimate from this site’s engine. Checked in October 2026. This is an independent information site: we provide no services, we do not represent the CRA or any organization, and we do not guarantee that anything here is accurate or current. We accept no liability for decisions based on it. Check the official source before you rely on it. See the full disclaimer.
Frequently asked questions
Can the CRA reassess me twice for the same year?
Yes, as long as it's inside the normal reassessment period or an exception applies. Each change produces a new notice of reassessment. Your own T1 adjustment can trigger one too, so a year may end up with several notices, and the latest one replaces the earlier calculation.
Do I have to pay a balance while I am objecting?
The CRA normally delays collection of the disputed amount until 90 days after it sends its decision, with some exceptions. Interest still accrues on the balance, and paying part or all of it reduces the interest you're charged if the CRA upholds the reassessment.
What if I miss the 90-day objection deadline?
Individuals get the later of 90 days or one year after the filing due date, and you can ask for an extension within one year after the original deadline. You have to show you couldn't act, or that you always meant to object. Apply through your CRA account or write to the Chief of Appeals.
Does a reassessment mean I am being audited?
No. Many reassessments come from a late slip, a T1 adjustment or a document check. An audit is one possible cause, and it arrives with a letter asking for records. The explanation of changes on the notice tells you which line moved and why.
Can I ask for a refund for a year that is past the three-year limit?
As an individual you can request a reassessment to get a refund or reduce tax payable up to 10 calendar years after the end of the tax year. The request has to be made by then, so a 2019 year would have to be asked for by 31 December 2029.