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Is your property tax assessment too high?
Every assessment implies a market value — assessed value divided by your area's assessment ratio. If that implied value is higher than what your property would actually sell for, you may be paying tax on value that isn't there. This check shows the math assessors and appeal boards actually use.
Enter the assessed value and ratio — the ledger fills in from there.
How an appeal works, honestly
Appeals argue value, with evidence — usually recent sales of comparable homes showing the assessor's implied value is high. The process and window vary by county: your assessment notice lists the deadline, and it's often short (30 days or so from the notice date is common). The general shape everywhere: check the notice for errors first (wrong square footage or bedroom count is the easiest win), gather 3–5 comparable sales, file the county's form by the deadline, and make the value case.
Worth knowing: an appeal challenges your assessment, not your tax rate — and a successful one lowers the taxable base for years, which is why the hour of paperwork can be one of the best-paying hours a property owner has.
Common questions
Where do I find my assessment ratio?
On the assessment notice itself or your county assessor's website. Some places assess at full market value (100%); many assess at a fraction of it. The ratio is public — it's the denominator of the whole system.
What evidence actually wins appeals?
Recent sales of genuinely comparable homes — similar size, age, and location — that sell for less than your implied value. Errors in the property record (square footage, bedroom count, lot size) are the other reliable winner: they're checkable facts, not opinions.
When is the deadline?
It's county-specific and printed on your assessment notice — often a short window from the notice date. If you're reading this with a fresh notice in hand, check that date first; everything else can be assembled inside the window.
Is it worth appealing for a small gap?
The math is the guide: gap × your effective tax rate = roughly the annual savings. A $20,000 over-assessment at a 2% effective rate is about $400 a year, every year, for an hour of paperwork. A $3,000 gap usually isn't worth the afternoon.
Not legal advice. This tool does the arithmetic; it doesn't know your county's procedures or deadlines — your assessment notice and county assessor's site are the authority on those. Nothing here is legal or tax advice.
What to do next
- Landlord? The $19 Rent Increase Report — the same comparable-sales thinking, applied to what your rental should earn.
- Rent increase calculator — percent, new rent, and your state's rules — free.
- Illinois landlord guides — deposit law, local licensing, and more — statutes cited.