Markham Property Tax Assessment Appeals — How to Challenge Your MPAC Valuation and Lower Your 2026 Tax Bill

Every four years, the Municipal Property Assessment Corporation (MPAC) updates property assessments across Ontario, and the 2026 cycle is generating significant anxiety among Markham homeowners. With Markham's real estate market having shifted substantially since the last assessment date, many homeowners are opening their tax notices to find their assessed values — and consequently their property taxes — have increased dramatically. Michael John Lau, Markham's top REALTOR® and a CPA/CMA, explains that MPAC's assessment is not the final word, and there is a formal, free legal process to challenge it.

How MPAC Determines Your Markham Home's Value

MPAC does not determine your property tax rate; they determine your property's assessed value. The City of Markham then applies its tax rate to that assessed value to calculate your actual tax bill. MPAC determines your assessed value by analyzing sales of comparable properties in your neighbourhood, adjusting for differences in lot size, age, square footage, renovations, and location. The critical detail most homeowners miss is the valuation date. MPAC's 2026 assessments are based on the property's market value as of a specific historical date (typically January 1, 2025), not the current market value today.

The Financial Reality — Why Your Assessment Might Be Wrong

MPAC's mass appraisal model is highly automated and relies on broad data sets. It frequently misses critical nuances that affect individual property values in Markham. Common errors include:

• Incorrect square footage or room counts: MPAC's records may not reflect recent finished basement renovations or accurate above-grade measurements.
• Flawed comparable sales: MPAC may have compared your Markham Village home to a sale in a completely different neighbourhood with different school catchments or lot premiums.
• Failure to account for negative factors: Proximity to commercial zoning, busy roads, or power lines that depress market value but are not fully weighted in MPAC's algorithm.
• Over-adjustment for market peaks: If your neighbourhood experienced a brief spike in sales prices that has since corrected, MPAC's valuation date may capture an unrepresentative peak.

The Request for Reconsideration (RFR) Process

If you believe your MPAC assessment is too high, you must file a formal Request for Reconsideration (RFR). This is not a simple phone call; it requires a documented submission. The process is free, and you can file it online directly through the MPAC website. When you file an RFR, you must provide evidence supporting your claim. The most effective evidence is a list of at least three to five comparable properties in your specific Markham neighbourhood that sold for less than your assessed value as of the valuation date. As a REALTOR®, I can pull this exact comparable sales data for you to include in your RFR submission.

What Evidence Actually Works in a Markham MPAC Appeal

MPAC adjudicators respond to data, not emotion. Simply stating that your taxes are too high will result in a denial. The evidence that successfully lowers assessments in Markham includes: recent arm's-length sales of truly comparable properties in the same neighbourhood; photos documenting functional obsolescence or needed major repairs (like an aging roof or foundation issues) that MPAC's model did not factor in; and professional appraisals for unique properties where automated comparables fail. If MPAC denies your RFR, you have the right to appeal to the independent Assessment Review Board (ARB), which functions like a court but is designed to be accessible to homeowners without lawyers.