In short
In Ontario, the Municipal Property Assessment Corporation (MPAC) sets it. It often sits well below today's market value and ignores your recent renovations.
The number is for taxes only. Price your home on recent sales, not on your assessment notice.
Who sets it in Ontario
The Municipal Property Assessment Corporation, or MPAC, assesses every property in Ontario. Municipalities, including the City of Ottawa, use that number with their tax rates to calculate property tax.
Your assessed value is for tax purposes only. It doesn't tell you what your home would sell for today, and lenders don't use it to decide how much to lend. Appraisers and buyers look at today's sales instead.
MPAC mails a Property Assessment Notice when your assessment changes. You can also look up your property's details, and similar homes nearby, through MPAC's AboutMyProperty service.
Why it's so far from market value
Ontario's province-wide reassessment has been postponed since the pandemic. As of 2026, assessments are still based on what properties were worth on January 1, 2016, according to MPAC.
That's why most assessments look low next to today's prices. MPAC does update a property's assessment when something changes, such as an addition, a new build or a change in use, but values are still measured against the 2016 date.
A low assessment doesn't mean you pay less than your neighbours. Taxes are shared based on relative values, so what matters is how your assessment compares to similar homes.
If your home rose in value faster than the average since 2016, your share of taxes may have shifted, but only after a future reassessment would that show up.
If you think your assessment is wrong
You can ask MPAC to review it through a free Request for Reconsideration. The deadline is printed on your assessment notice, so act soon after it arrives.
If you disagree with MPAC's answer, you can appeal to the Assessment Review Board within 90 days of MPAC's decision. Bring sales of similar nearby homes to support your case.
Check the facts MPAC has on file first, such as square footage, lot size and number of bathrooms. Errors in the details are among the easiest things to correct.
Common questions about assessed value
What is assessed value vs market value?
Assessed value is MPAC's figure for calculating property tax, while market value is what a buyer would pay today. In Ontario they're usually far apart because assessments still use a January 1, 2016 valuation date. Price a home on recent comparable sales, not on its assessment.
Why is my MPAC assessment so low?
Because Ontario assessments are still based on January 1, 2016 values. The province postponed the planned reassessment during the pandemic, and MPAC confirms 2026 property taxes continue to use 2016 values. Prices have risen a lot since then, so the gap is normal.
When will Ontario reassess property values?
No new valuation date had taken effect as of 2026, and taxes that year still use January 1, 2016 values. The timing of the next province-wide reassessment is up to the Ontario government. Watch MPAC's website for announcements. Until then, the 2016 values stay in place.
How do I appeal my property assessment in Ontario?
Start by filing a free Request for Reconsideration with MPAC before the deadline on your notice. If you still disagree after MPAC reviews it, you can appeal to the Assessment Review Board within 90 days of MPAC's decision. Recent sales of similar homes make the strongest evidence.
Sources
General information for Ontario, updated October 2026. Not legal, tax or mortgage advice. Rules change, so confirm with your lawyer, lender or the source above before you rely on it.