Updated Checked by the Tax-Services.ca editorial team How we check
A notice of assessment is the CRA’s summary of your return after it has processed it, and the first thing to check is whether it says “Refund”, “Amount due” or “Balance: Nil”. If you disagree with it, the CRA’s notice page gives you 90 days from the date on the notice to register a formal dispute, and for many individuals the objection rules give more time. Put the 90 day date in your calendar the day you open it, and treat anything later as a bonus.
What does a notice of assessment tell you?
It shows what the CRA calculated from the numbers you filed. If the CRA later changes your return, you get a notice of reassessment instead. You’ll find either one in your CRA online account under Tax returns or Mail, or in the post at the address the CRA has on file.
| Section of the notice | What to look at |
|---|---|
| Account summary | Refund, amount due or nil balance |
| Tax assessment details | Line amounts against your filed return |
| NETFILE access code | Eight characters, used to file online next year |
| Registered plan statements | RRSP deduction limit, Home Buyers’ Plan, Lifelong Learning Plan, FHSA details |
Most people glance at the refund and file the notice. Fair enough, but the deduction limit on it is the one number you’ll want again in February.
How do you check a notice of assessment?
Put your return and the notice side by side and go line by line. Income first, then deductions, then credits. A missing slip is the usual culprit: a T4 or T5 you forgot shows up as extra income on the notice.
A quick reasonableness check helps too. On $60,000 of employment income in Ontario, our income tax calculator gives about $8,320 of income tax before other credits. If your notice shows something wildly different, find the line that explains it. The tax refund calculator does the same job from the refund side.
If the notice is missing something of yours, the CRA says you can make changes to your return. That’s a correction, not a fight, and it’s usually the right move when the error is yours.
When can you object to the assessment?
Only when you think the CRA got it wrong. The CRA’s objection guide lists what to send: your name and address, a phone number, the date of the notice, the tax year and account number, the facts and reasons, and copies of your documents. You can send it through My Account, by mail or fax with form T400A or a signed letter, or by hand at a tax services office.
Now the deadline, and here’s a wrinkle. The CRA’s notice page says 90 days from the date of the notice. Its page on filing an income tax objection says an individual has the later of one year after the filing deadline for the return and 90 days from the date of the notice. For a TFSA or RRSP matter and for corporations, it’s the 90 days. The two pages word it differently, so work to the 90 day date unless you’ve confirmed the later one applies to you.
An example. Your notice is dated 15 June 2026. Ninety days takes you to 13 September 2026. That’s the date to beat if you’re not sure.
Miss it and you may still apply for an extension, but only if you couldn’t object for reasons outside your control, and no later than one year after the original deadline. Don’t plan around that.
What if the notice says you owe money?
You can pay the balance in full or arrange to pay over time. Doing nothing is the worst option. The CRA’s guide says interest keeps running on an amount while it’s in dispute, and that partial payments can cut the interest that builds up.
The CRA normally holds off collection on a disputed amount until 90 days after it sends its decision. That doesn’t stop the interest, so objecting is not a free delay.
If you owed this year because too little came off your pay, look at the tax instalments calculator. It helps you see whether paying quarterly would have avoided the bill. And if the notice gives you a larger RRSP room than you expected, try the RRSP calculator to see what a contribution would save.
Where should you keep it?
Save a copy of every notice with the return it belongs to, in the same folder, year after year. Tax time goes much faster when last year’s deduction limit and NETFILE code are sitting right there instead of buried in an old email. A PDF from My Account takes seconds to download, and it’s the closest thing to a free insurance policy for your tax file.
Mistakes to avoid with a notice of assessment
Don’t ignore a notice because the refund arrived. Don’t throw it out either. You’ll want it if the CRA asks questions later, and the NETFILE code and deduction limits are on it.
Don’t file an objection when a simple change to your return would do. And don’t rely on a date you worked out in your head: use the date printed on the notice.
We haven’t covered what the CRA’s review or audit letters look like, or the interest rate on a balance, because we couldn’t confirm the current details on an official page. Check the CRA’s pages for those.
How we checked the figures
The notice contents and the 90 day rule come from the Canada Revenue Agency‘s page on notices of assessment and reassessment. The individual one year rule, extension rules and interest during a dispute come from its objection rights guide (P148) and the objection page linked above. The tax estimate comes from our calculator, which uses 2026 federal and Ontario rates.
Frequently asked questions
What is a notice of assessment?
It's the CRA's summary of the amounts it calculated from your return. A reassessment notice follows if the CRA changes the return.
Where do I find my notice?
Sign in to your CRA account and go to Tax returns or Mail, or wait for the paper copy.
How long do I have to object?
The CRA's notice page says 90 days from the date on the notice. Its objection guide gives individuals the later of 90 days and one year after the filing deadline.
Does interest stop if I object?
No. The CRA says interest still applies to an amount owing while it's in dispute.
What if the notice leaves out an amount?
You can make changes to your return. You don't need a formal dispute for your own mistake.
- How to file your tax return in Canada: steps and dates
What to gather, when your return is due and how to file in Canada, from the first slip to the notice of assessment that closes the year