If you live in Ontario, your property tax bill starts with one number: your MPAC assessed value. MPAC doesn’t set your tax rate. It sets the assessed value that your municipality applies those rates to. That’s why two neighbours can pay different tax bills even under the same rate.
Think of MPAC as the measurement system, not the price tag. The tax rate is the price tag.
What MPAC is actually doing
MPAC (Municipal Property Assessment Corporation) estimates your property’s value using a standardized system so municipalities can apply rates consistently. It’s not trying to match today’s listing price. It’s trying to create a fair, province‑wide baseline for taxation.
That’s why the assessed value often looks “off” compared to what you’d sell for.
Why your MPAC number often doesn’t match “the market”
A common reaction is: “This number feels wrong.” That’s normal.
Ontario’s province‑wide reassessment has been postponed, so for the 2026 tax year MPAC assessments are still based on January 1, 2016 values unless a property has changed (new build, renovation, change in use, etc.). That delay alone explains a lot of the mismatch.
MPAC values also move on a cycle. In a fast‑rising market, MPAC can look low. In a cooling market, it can look high. Neither automatically means the assessment is incorrect — it means it’s not a live appraisal.
If you’re comparing your MPAC value to a realtor’s estimate or a neighbour’s recent sale price, you’re comparing two different tools.
How the assessment affects your tax bill
Your municipality sets the tax rates, then applies them to your MPAC value. If your assessed value rises but everyone else’s rises too, your share of the tax base might not change much. Rates can shift to keep total municipal revenue on target.
So a higher MPAC value doesn’t always mean a proportionally higher bill — but it does raise the base that rates apply to.
A simple way to think about it:
- MPAC value = the base
- Tax rate = the multiplier
- Bill = base × multiplier
Appeals: what changes and what doesn’t
An MPAC appeal can change your assessed value. It does not change the municipal tax rate.
If an appeal lowers your MPAC value, your tax bill goes down because the same rate is applied to a smaller number. Appeals take time and usually require evidence (comparable properties, property details). For many homeowners, the tradeoff is effort vs potential savings.
A useful mindset: you’re challenging the assessment, not the tax.
Practical takeaway
Use MPAC as the baseline for taxes, not as your home price.
When you use the property tax calculator, enter the assessed value shown on your MPAC notice or tax bill. That’s the number the municipality uses — and it’s the only number that will make your estimate line up with your actual bill.