An assessment appeal in Ontario runs through two separate systems: MPAC, which sets the assessed value, and the Assessment Review Board, an independent tribunal that decides disputes about it. Here is the process end to end for a commercial, industrial or multi-residential property, from the notice to a decision.
Who is involved
Three parties sit on a typical file. MPAC, the Municipal Property Assessment Corporation, sets the assessed value your taxes are based on and is the respondent when you appeal it. Your municipality collects the tax and is usually a party to the appeal too, since the assessed value feeds directly into the tax bill it sends. The Assessment Review Board, part of Tribunals Ontario and separate from both, hears the dispute and decides it.
The notice that starts the clock
Every property in Ontario carries an assessed value set by MPAC. For the 2026 tax year, that value is still based on January 1, 2016 current values, and no new province-wide reassessment has been announced (MPAC, the assessment cycle). Outside of a general reassessment, MPAC only mails a new notice when something about a specific property changes, for example new construction, a demolition, a severance, an ownership transfer or a change in use. In its most recent mailing, that meant more than 618,000 properties across Ontario received a notice (MPAC, notice mailing). Whatever kind of notice you receive, annual, change, amended, supplementary or omitted, it is what starts one of the appeal deadlines.
Two ways to challenge an assessment
There are two starting points. You can ask MPAC to look again through a Request for Reconsideration (RfR), which is free and which MPAC aims to answer within 180 days, or you can appeal directly to the Assessment Review Board. Residential, farm and managed forest properties must file an RfR before they can appeal. Commercial, industrial, multi-residential and other business properties do not have to: they can go straight to the Board (MPAC, Request for Reconsideration and Appeals). Which route makes more sense for a given roll number is its own question, covered in RfR or straight to the Board.
Filing with the Assessment Review Board
Once you have decided to appeal, or MPAC has issued its RfR decision and you still disagree, the appeal itself follows a set path.
- File within the deadline. Appeal the current year’s assessment to the Board by March 31, or within 120 days of a change, amended, supplementary or omitted notice. If you filed an RfR first, you have 90 days from the date MPAC mails its decision to appeal.
- Pay the filing fee. The Board charges $318 per roll number for multi-residential, commercial, industrial and other non-residential properties, $10 less if you e-file (Tribunals Ontario, filing an appeal).
- Receive an acknowledgement and a Schedule of Events. The Board confirms your appeal and sets the dates that will govern the file, including a commencement date.
- Attend a case management or mandatory meeting. The parties, MPAC, the municipality and you, meet to identify the issues and see whether the file can be narrowed or resolved early.
- Exchange disclosure. Each side files the evidence, appraisals and comparable data it intends to rely on, by the dates the Schedule of Events sets.
- Try to settle. Most files are resolved at this stage through a negotiated value, recorded in writing as Minutes of Settlement, which the Board then issues as its decision without a hearing.
- Hearing and decision. If the parties cannot agree, the Board holds a hearing and issues a written decision.
You can represent yourself at the Board, or be represented by a licensed paralegal, lawyer or authorized agent. BrookLex’s appeals are led by a licensed paralegal with the Law Society of Ontario. See James Brook.
How most appeals actually end
Most Assessment Review Board files do not reach a hearing. MPAC, the municipality and the property owner negotiate a value all three can accept, put it in writing as Minutes of Settlement, and the Board issues that agreement as its decision. A hearing is what happens when a settlement is not reached, not the normal outcome of filing an appeal.
How long it takes
The Board does not publish a fixed timeline for every file. Once your appeal is accepted, it assigns a Schedule of Events specific to that appeal, so the length depends on the property, the issues raised, and how quickly disclosure and any settlement discussions move (Tribunals Ontario, filing an appeal).
What it costs to file
Filing itself costs $318 per roll number for a business property, $10 less if you e-file. That is separate from the professional fee for building and arguing the case. See fees for how BrookLex charges, and assessment appeals for what we do at each stage above.
What the parties can appeal
It is not only owners who appeal. A municipality can appeal an assessment it believes is too low, and MPAC can be a party defending its own number against either side. On a file where the municipality is the one pushing for a higher assessment, the property owner is the one defending the existing value, which changes how a case is built even though the process above still applies. See assessment appeals for how BrookLex handles a file either way.
If your notice or your type of property raises a question this guide does not answer, see questions owners ask, check key dates for the specific deadline that applies to you, or contact us before a deadline passes.