How do I dispute my Ontario property tax assessment?

Property assessments in Ontario are set by the Municipal Property Assessment Corporation (MPAC), which assigns each property a value for property tax purposes. If you believe your assessed value is too high — and therefore your property taxes are too high — you have a formal process for challenging it.

The first step is to file a Request for Reconsideration (RFR) with MPAC. An RFR asks MPAC to review the assessment and provide a detailed explanation of how they calculated it. You can compare your assessed value to sales data and assessments for similar properties in your neighbourhood using MPAC's AboutMyProperty portal. MPAC must respond within a set period, and they may adjust the assessment, maintain it, or increase it (though increases based on an RFR are uncommon).

If you are not satisfied with MPAC's response to the RFR, the next step is an appeal to the Assessment Review Board (ARB), an independent provincial tribunal. ARB appeals have filing deadlines and require you to present evidence — typically comparable sales or an independent appraisal — supporting your position on value.

Property owners often succeed in reducing assessments when they can show comparable properties assessed at lower values for similar physical characteristics. The ARB process is accessible without a lawyer, but professional assistance from an agent or lawyer familiar with assessment appeals can improve your chances on complex files.