Why this happens — even when the market cooled
County assessors use mass-appraisal models. They look at broad sales data from the prior 12–24 months, apply it to a rigid formula, and publish new values in batch. When the model catches up to a hot market just as the market turns, assessments lag — and they lag upward. Your value may reflect last year's peak, not today's reality.
On top of that, reassessment cycles are not synchronized with market cycles. Some counties reassess annually; others every two, three, or five years. If your county finally got to you after skipping a cycle, you may be absorbing multiple years of compressed increases in one notice — even if prices in your zip code have been flat for six months.
The 25–45 day window
Every state sets a short deadline to file an appeal after your notice is mailed — typically between 25 and 45 days. Miss it and you're locked into the new assessment for the full tax year. No extensions, no appeals-to-the-appeal. The clock starts the day the notice is postmarked, not the day you read it.
Check your notice today
The deadline is printed on your notice of assessment. If you've set it aside, pull it back out — the window is almost certainly shorter than you think.
The evidence you need
Boards respond to data, not frustration. You don't need a lawyer. You need a clear, numerical argument that your assessed value is higher than recent market evidence supports.
3–5 recent comparable sales
Similar homes in your neighborhood — within 15–20% of your square footage and age — that sold within the last 6–12 months for less than your new assessed value.
Your prior assessment and this year's
Show the board the percentage increase year over year. If your assessment jumped 15% while local sale prices were flat or down, the gap itself becomes evidence.
A market trend chart for your zip code
Zillow, Redfin, or Realtor.com all publish a median sale-price trend for any zip code. Print the 12-month chart showing flat or declining prices.
Your property record card
Free from the county assessor's website. Errors — wrong square footage, a bathroom that doesn't exist, a pool that's been filled in — are pure fact arguments with no market analysis required.
How Fairmark handles it
When you run a Fairmark analysis, we pull your current assessment, your prior assessment, recent sales of comparable properties in your area, and your county's filing deadline — all at once. If there's a gap between the assessed value and market evidence, we build the case for you.
With Fairmark Complete, we file the appeal, assemble the evidence packet, and represent you through the informal review. You don't attend a hearing. You don't fill out forms. You get status updates every two weeks until the case is resolved. If we don't reduce your assessment within 90 days, you get a full refund.
Got a notice with a number that looks wrong?
Run a free Fairmark check before the appeal window closes. We'll show you the market evidence in seconds.
If your assessment jumped, do this today
- Find the deadline printed on your notice of assessment.
- Pull 3–5 recent sales of similar homes in your neighborhood.
- Download your county property record card and check for errors.
- File the appeal — or run a free Fairmark check and let us file it.