Article
Ontario section 357 and 358 tax applications
Updated September 22, 2026 · 3 min read
Not every Ontario property tax problem goes to MPAC. When something happens to your property during the year, or the roll contains a plain error, the Municipal Act lets you apply to your municipality to cancel, reduce or refund taxes. These are known by their section numbers, 357 and 358.
Section 357: something changed during the year
Section 357 covers specific events listed in subsection 357(1) of the Municipal Act. They include, for example:
- a change in tax class, such as when part of a property stops being used in a way that carried a higher rate;
- a building razed or damaged by fire, demolition or otherwise;
- certain other listed events, for example some repairs or renovations that prevented normal use of a property.
Check your notice
Deadline: the application goes to the municipal treasurer on or before the last day of February of the year after the tax year it concerns. A deadline that lands on a weekend or holiday moves to the next business day.
Example (dates from the rules engine's test cases)
Section 358: a gross or manifest error in the roll
Section 358 is for taxes that were too high because of a gross or manifest clerical or factual error in the assessment roll, the kind of mistake that is obvious once pointed out. Examples include a house recorded on the wrong lot or a clear transcription error.
Timing for roll errors: you apply between March 1 and December 31 of a year, for taxes of one or both of the two preceding years.
Leave room at the end of that window. An application made in the following January reaches only the two years before that January, so the earlier year you meant to cover can drop out. We therefore treat the last business day on or before December 31 as the deadline.
Timing for errors in a supplementary or omitted assessment: on or before December 31 of the second year after the assessment was made.
Section 358 has limits. It can't generally be used for a year whose assessment was already under appeal, subject to exceptions. It isn't a way to argue that the value was too high in general. That's what the Request for Reconsideration is for. See Ontario's RFR, explained.
What happens after you apply
The municipality reviews the application, sometimes with MPAC's input, and may hold a meeting where you can speak. If it's approved, the taxes are cancelled, reduced or refunded for the affected period. Any refund or credit goes to you, the owner, not to us.
Why these applications are worth knowing about
They're often missed. Owners who had a fire, demolished a garage or converted part of a building may keep paying the old amount, simply because nobody told them the Municipal Act has a remedy.
How we help
We check whether one of the listed grounds appears to apply, gather the evidence (permits, photos, insurance reports, dates) and prepare the application for the treasurer. A $79 upfront review-and-filing fee, and our share applies only if taxes are reduced or refunded. See the fee page.
If your situation doesn't fit, we'll tell you.
Evidence that helps an application
- Dates. When the event happened: the fire, the demolition, the start and end of the work.
- Proof of the event. Demolition or building permits, a fire department or insurance report, dated photos.
- Proof of use. For a class change, evidence of how the property was actually used and from when.
- The tax bills for the period you're asking about.
Applications are decided on the record. The clearer the dates and the proof, the easier it is for the municipality to say yes.
Check your assessment, free
The assessment check is free and you don't need to create an account to see your result.