Your Ontario property assessment, explained

Ontario is different from the western provinces in two ways. For the 2026 tax year, Ontario assessments are still based on values as of January 1, 2016. And a successful appeal usually lasts: a reduction carries through the rest of the assessment cycle. That's why we focus on situations where Ontario owners can act today, and why we're careful.

An issue that has been settled or decided generally can't be argued again later in the same assessment cycle, so we only file when the case is strong.

You may be fairly assessed. If you are, we'll tell you.

Who we help in Ontario

• New homes. MPAC reported assessing about 81,000 new homes in 2025. Each gets a fresh notice, often a supplementary or omitted assessment that produces a bill going back to when you moved in.
• Specific errors in the facts MPAC has on file, such as the wrong square footage, number of storeys, basement or lot.
• Municipal tax applications under sections 357 and 358 of the Municipal Act, for example after a demolition, a fire or a change of tax class, or to fix a clear error.
• Owners in higher-rate municipalities, where a given reduction is worth more.

Step one is always a Request for Reconsideration (RFR)

For a home, you ask MPAC to reconsider before anything else. A residential owner can't appeal to the Assessment Review Board without a timely RFR.

Your RFR deadline depends on the notice you received:

• Supplementary or omitted assessment (typical for new homes): 120 days after the issuance date printed on the notice.

  Source: Assessment Act, R.S.O. 1990, c. A.31, s. 39.1(3) (notice under s. 35(1) for omitted/supplementary assessment: 120 days after the issuance date on the notice)

• Annual notice: March 31 of the tax year.

  Source: Assessment Act, R.S.O. 1990, c. A.31, s. 39.1(1.1) (RFR no later than March 31 of the taxation year); Legislation Act, 2006, s. 89(1)

• First year of a province-wide reassessment: 120 days after the issuance date on the notice.

  Source: Assessment Act, R.S.O. 1990, c. A.31, s. 39.1(1.2) (first taxation year of a general reassessment: 120 days after the issuance date on the notice)

In every case, a deadline that falls on a weekend or holiday moves to the next business day. Look for the issuance date on the notice itself, not the day it arrived.

The RFR is the review step. We ask the assessor to review your assessment first. We file an appeal only to protect your rights if the review isn't resolved in time.

Getting MPAC's data

MPAC's comparables for your home are behind your owner login. We'd rather not hold your access key. Our preference is MPAC's own process for authorizing a representative. Our second choice is for you to send us your notice. We use your login only if neither works, once per season, and we delete it within a short, fixed period.

If MPAC says no: the Assessment Review Board (ARB)

If you disagree with MPAC's RFR decision, you can appeal to the ARB, an independent tribunal. The appeal is due 90 days after the issuance date on MPAC's decision. If MPAC doesn't decide in time, the Act sets a fallback date instead.

Source: Assessment Act, R.S.O. 1990, c. A.31, s. 40(3) (residential/farm/managed forests: RFR is a precondition of appeal); s. 40(3.1); s. 40(5) para 1 (90 days after the issuance date on MPAC's notice of reconsideration), para 2 (90 days after the notice should have been provided under s. 39.1(7): 180 days after the request, 240 if MPAC notified an extension)

Source: Assessment Act, R.S.O. 1990, c. A.31, s. 40(3), 40(5) para 1-2; s. 39.1(8) (MPAC notice for omitted/supplementary RFR due 180 days after the request — no extension)

ARB appeals are handled by a lawyer or paralegal licensed by the Law Society of Ontario. We take a file to the ARB only when the evidence justifies it. If your file goes to a hearing, a person represents you. Software never appears in front of a board.

Municipal applications: sections 357 and 358

These go to your municipality's treasurer, not to MPAC. They can lead to cancelled, reduced or refunded taxes.

• Section 357 covers specific events during the year. The grounds are listed in s. 357(1) of the Municipal Act. They include, for example, a change in the property's tax class and a building razed or damaged by fire, demolition or otherwise. The application is due by the last day of February of the following year.

  Source: Municipal Act, 2001, S.O. 2001, c. 25, s. 357(3) (application filed with the treasurer on or before the last day of February of the year following the year in respect of which it is made); Legislation Act, 2006, s. 89(1)-(2)

• Section 358 covers a gross or manifest clerical or factual error in the assessment roll. For a roll error, you apply between March 1 and December 31 of a year, for taxes of one or both of the two previous years.

  Source: Municipal Act, 2001, S.O. 2001, c. 25, s. 358(1)(a), (3) (gross or manifest clerical/factual error in the roll: application between March 1 and December 31 of a year, for taxes of one or both of the two preceding years)

  For an error in a supplementary or omitted assessment, the deadline is December 31 of the second year after the assessment was made.

  Source: Municipal Act, 2001, S.O. 2001, c. 25, s. 358(1)(b), (3.1) (error in an assessment under s. 33 or 34 of the Assessment Act: on or before December 31 of the second year following the year in which the assessment was made); Legislation Act, 2006, s. 89(1)

How our Ontario fee works

Because a reduction lasts, our Ontario fee covers more than one year. In Ontario, it is 30% of the tax saving for 2.5 savings-years, collected in instalments once per tax year when your bill shows the saving, only if your assessment goes down. Instalments stop if you sell the home or if the province announces a reassessment. The fee page has a worked example.

Canada Tax Appeal is a private company. We are not a government body or an assessment authority and are not affiliated with MPAC or any municipality.