Evidence that works when you challenge an MPAC assessment

The question your evidence must answer

MPAC asks it in one sentence: "Could I have sold my property on January 1, 2016 for the assessed value stated on my Notice?" Every piece of evidence should help answer it. The value is the 2016 value, but for the property as it stands now, including major changes made since.

MPAC uses mass appraisal: it applies results drawn from area sales to your property's features. An error in those features (size, age, basement) flows straight into the value.

What MPAC asks for

On its reconsideration page, MPAC lists the evidence to gather:

• Photos showing differences between MPAC's records and the property in its current condition.
• Sale information on your property or comparable properties.
• Assessed values of comparable properties, found in AboutMyProperty. You can attach your "My Favourites Report" from the Browse My Neighbourhood section.
• Recent appraisals.
• Zoning information.
• Estimates for significant repairs, such as cracked and leaking foundation walls, flood damage, termite damage or a sagging roof line.

Data errors: the simplest ground

MPAC names this ground outright: "The property data on your Notice of Assessment or on MPAC AboutMyProperty is incorrect." Its examples are building size and land area. Compare each item in AboutMyProperty with your plans, your survey and your permits.

Items to check: living area, lot size and frontage, year built, number of storeys, finished or unfinished basement, garage, pool, number of bathrooms. An inflated figure pushes the value up. A missing feature can push it up too if MPAC finds it, which is why you should check everything before filing.

Comparable sales: which ones count

MPAC uses open market sales only: "MPAC only includes open market transactions within its mass appraisal process." It excludes, among others, sales between family members, forced sales (foreclosure, family break-up, expropriation) and sales from a builder.

Prices are time-adjusted to reflect the market on the valuation date. A 2015 or 2016 sale of a similar home in the same area therefore weighs far more than a 2025 sale. If you rely on a sale far from 2016, explain how you bring it back to January 1, 2016, or leave that work to an appraiser.

Your neighbour's assessment: in Ontario, it counts

This is a clear difference from Quebec. Section 44 (3) of the Assessment Act tells the ARB to determine current value, then look at how similar lands nearby are assessed and adjust the assessment "to make it equitable with that of similar lands in the vicinity if such an adjustment would result in a reduction."

In short, if truly similar properties are assessed lower, that is a valid argument, and it only works downward. Choose comparables close in type, size, age and location.

What does not work

The amount of your taxes. The grounds of appeal in section 40 (1) cover value, classification and who is on the roll. MPAC reminds owners that assessment and taxes "are not the same thing." To dispute the tax bill itself, the ARB points to a separate process (a tax application).

Today's market. An offer you received in 2026 or an asking price from 2025 says little about 2016.

A general impression. The Act requires the request to set out its basis and "all relevant facts" (s. 39.1 (4)). At the ARB, late evidence is not admitted.

At the ARB, the burden is on MPAC

When value is at issue, section 40 (17) puts the burden of proof on MPAC: "the burden of proof as to the correctness of the current value of the land rests with the assessment corporation." That burden shifts to the owner who refuses an inspection or fails to provide requested information (s. 40 (18)). Cooperate, and keep a copy of everything. Next, see after you appeal and the complete guide.

Frequently asked questions