The MPAC RfR Deadline Is March 31: What Happens If You Miss It

Ontario's assessment review system is forgiving about almost everything — it's free, it's plain-language, you can represent yourself — except time. The deadlines are hard, and missing one closes the tax year.

Here's exactly how the clocks work, what missing one actually costs, the narrow exceptions, and the calendar setup that makes this a solved problem forever.

The two clocks

Clock 1 — the general deadline: March 31 of the tax year. Every tax year has its own RfR window, and it closes March 31 of that year. The deadline for the 2026 tax year was March 31, 2026. Each new tax year opens a fresh window for that year.

Clock 2 — the notice clock: 120 days from issuance. If MPAC mails you a Property Assessment Notice (triggered by a change — construction, renovation, classification, severance), your window to challenge it is 120 days from the issuance date printed on the notice. Notices commonly go out in the fall, which typically lands the 120-day mark in a similar early-spring range — but the printed date governs, not the calendar pattern. Read the notice; the date is on it.

When both could apply, the safe habit is simple: act on whichever deadline arrives first.

What missing it actually costs

Three things, one of them permanent:

That tax year is closed. You pay the full year's taxes on the uncorrected assessment. On a typical over-assessment — say $55,000 high at a ~1% effective rate — that's roughly $550 that cannot be recovered through the review process. (Run your own number here.)

The overpayment is not refundable later. Winning next year's review corrects next year. It does not reach back. This asymmetry is the entire reason to check your assessment on your schedule rather than the deadline's.

Nothing else is lost. This is the part people get wrong in the other direction: missing a year does not weaken your future case, flag your file, or forfeit anything except that year's money. The next window opens and your evidence is exactly as strong.

The narrow exceptions

Two routes exist outside the RfR clock. Both are narrow — treat them as facts to know, not plans to rely on.

Municipal applications for cancellation or refund. Ontario's Municipal Act lets owners apply to their municipality (not MPAC) for tax cancellation or refund in specific enumerated situations — a building demolished or razed by fire, a property that changed class or became exempt, sickness or extreme poverty, and gross or manifest error of a clerical or factual nature. These applications carry their own strict deadlines (generally the last day of February of the following year for current-year events, with a limited lookback for gross clerical errors). The key limitation: "the model valued my house inequitably" is a valuation opinion, not a gross clerical error. This route rescues the file that says 3,100 sq ft on a 1,600 sq ft house; it does not rescue an ordinary equity argument that missed March 31. If you think you genuinely qualify, contact your municipality's tax office about its application process.

A new notice restarts a clock. If your property changes and MPAC issues a new Property Assessment Notice, that notice carries its own 120-day window. You can't manufacture this, but if one arrives, it's a live opportunity — open it the day it comes.

The calendar fix (five minutes, permanent)

1. Recurring annual reminder — early January: "Check MPAC assessment — RfR deadline March 31." January, not March: the check takes an evening and the filing is better done with weeks of slack, not hours. (The evening in question.)
2. A rule for mail: any envelope from MPAC gets opened the day it arrives, and if it's a notice, the issuance date + 120 days goes straight into the calendar.
3. If you find a case in January: file in January or February. Nothing improves by waiting for March, and MPAC's queue only grows toward the deadline.

If you're reading this in April with a case in hand

The honest sequence:

1. Confirm which year you're actually in. If a recent notice gave you a 120-day clock, you may still be inside it — check the printed date before assuming you've missed anything.
2. Check the gross-error route only if your situation is a documented clerical/factual error of the "wrong building on file" magnitude.
3. Otherwise, aim at the next tax year — now, not next March. Do the verification work today: pull your file, document any errors, build the comparables table. When the next window opens you file in its first weeks, and the missed year becomes the last one you overpay rather than the first of several.

Frequently asked questions

Does the March 31 deadline move if it falls on a weekend?

Statutory deadlines falling on weekends or holidays are generally treated as extending to the next business day, but never plan around that — the only deadline strategy that works is not being near it.

Can I file an RfR early, before I even get a bill?

You don't need a bill in hand — the window for a tax year is open well before March 31, and your assessment (the thing under review) is already on file. Early in the year is the ideal filing time.

I missed the deadline but my neighbour filed and won. Does their result help me?

Not for the closed year. For the next window, it's excellent news: a successful comparable review nearby is evidence the model was off in your pocket of the neighbourhood, and their corrected assessment becomes a data point in your table.

Is there any deadline on the ARB side I should know about now?

Yes — if you do file an RfR and want to appeal MPAC's decision to the Assessment Review Board, a separate strict deadline runs from the date of MPAC's decision (it's stated with the decision). The system is deadlines all the way down; the calendar habit above covers the first and most important one. More on the escalation path: RfR vs. ARB appeal.