Cook County property tax appeal

A Cook County appeal is argued on unequal treatment, not on market value

The engine runs Cook County as a uniformity case. Each comparable's ratio is its assessed value divided by its living area; the median of those, multiplied by your square footage, is what your assessment would be if you were treated the way your neighbours are. No sale price enters that chain anywhere, which is why the check still works on a street where nothing has changed hands in years.

No statutory ratio corridor constrains this board, so the size of the gap is the case. The thresholds that turn a gap into a recommendation are ours rather than the board's, and they are deliberately conservative: a gap under 5.0% of the implied fair assessment is treated as appraisal noise and returns “not worth it”, and a strong case needs a gap of at least 10.0%, high confidence, and an estimated annual overpayment of at least $200. Most homes come back “looks fair”, which is the honest result for most homes.

One caution belongs here rather than in a footnote. The Board of Review's published official rules do not enumerate permissible grounds, and the board describes its own work as hearing appeals of over-valuation — which is a market-value framing, not a uniformity one. Uniformity-first is what this county's rules file encodes and it has not been confirmed against a primary source, because the Assessor's site refuses automated requests. It is the highest-stakes unverified value in the file: it selects the entire ratio model, so if it is wrong the verdict is computed on the wrong basis rather than merely labelled oddly.

What are the appeal levels in Cook County?

Start at the first level. Each later one reviews the decision before it, so a case that was never made at the county board is hard to make afterwards.

1. 01Assessor's Office appeal (first level, online filing)
2. 02Cook County Board of Review
3. 03Illinois Property Tax Appeal Board (PTAB) or Circuit Court of Cook County

The last two are alternatives, not sequential steps: after the Board of Review you choose one of them, and choosing is the end of the choice.

There is no countdown on this page, and that is the correct answer

Cook County's filing deadline is not an interval anybody can compute from a notice. The window opens when your township's reassessment notices mail — Cook County's 38 townships open for appeal on a rolling calendar through the year, and the operative deadline is a close date each body publishes for each township, every session. The rules file carries 30 days after notice as its model, and that figure is a stated minimum rather than the rule: the Board of Review says townships are open a minimum of 30 days, and in the 2026 calendar the first township group opened on 3 August and closed on 1 September — a shorter span than that. Counting forward from your notice therefore overshoots, and overshooting a filing deadline by one day costs the year. Read your township's published close date; do not compute one.

A second date matters just as much and appears nowhere in the rules file. The Board of Review sets a separate evidence-submission deadline that falls after the filing deadline — for that same 2026 group, filing closed on 1 September and evidence was due on 11 September. A homeowner can file on time and still lose the appeal on evidence, and this site has no concept of that second deadline, so it cannot warn you when it approaches. Ask for both dates when you ask for one.

Nor does the ruleset record whether a mailed complaint is judged by its postmark or by the date it arrives — a distinction that decides whether posting on the last day works. New Jersey's answer has been read from a primary source and is stated on the Bergen page. Illinois's has not, so this page says nothing about it rather than guessing at the version that would sound more helpful.

Verification status of the deadline rule above: UNVERIFIED — confirm the current-year township calendar.

Filing costs nothing here, which removes one check on the verdict

No fee to file a residential appeal with the Assessor's Office or the Board of Review. A zero fee is good news for a homeowner and a complication for an honest verdict: one of the three tests that can return “not worth it” is whether the estimated first-year saving clears the filing fee, and against a fee of nothing that test can never fire. What stops a marginal case here is the 5.0% noise floor and the confidence score, and nothing else.

The free-filing claim is also only half-confirmed. It is verified for the Board of Review, which states plainly that filing there is free. The same sentence in the rules file extends it to the Assessor's Office, and that half has never been read from the Assessor, whose site returns a bot block to every automated request. If the Assessor charges, a verdict computed against a fee of $0 is comparing a saving against the wrong number.

Verification status of the fee: UNVERIFIED.

Which form do I file?

• Online residential appeal (Assessor's portal) fillable PDF
• Board of Review residential complaint fillable PDF

Neither entry is a downloadable complaint form. Residential filing at both levels is done through an online portal rather than a PDF, so these links open the office that runs the portal. There is no paper residential form to print at the Board of Review.

A Cook County comparison needs at least 3 comparable assessments, not sales

Residential appeals commonly rest on lack of uniformity — comparable homes in the same neighborhood and class assessed at lower values per square foot — or on recent sale evidence and characteristics errors. Photographs and comparable assessment printouts are accepted.

The check applies four hard filters before it computes anything: same property class, same neighbourhood or assessment area, living area within ±20% of yours, and an assessment inside this county's 18-month window. The survivors are ranked by similarity and the closest 8 are kept. Fewer than 3 survivors and no verdict is produced at all — every rejection is listed with the reason it was rejected, so a thin result reads as a thin result rather than a confident one.

The 18-month window is the weakest link in that chain. No published evidence-recency standard was found in any reachable Illinois source, so the figure is a modelling default rather than a rule the board enforces. Treat it as a filter this site applies, not as a limit the board would.

Verification status of the evidence standard: UNVERIFIED — confirm current evidence rules.

Is my assessment actually too high?

Run the free assessment check with Cook County's rules applied. It picks comparable homes, takes their median assessment ratio, and tells you honestly whether the gap is worth the paperwork and your afternoon. Most people are told not to file. The arithmetic is on the methodology page.

The Assessor's site is bot-blocked, so several values on this page are unverified

The estimated rate on assessed value in the table above — 20.0% — is unresolved, and it is the multiplier behind every dollar figure the check reports as an estimated annual overpayment. Cook's real burden is the assessment level multiplied by the state equalization factor the Illinois Department of Revenue re-strikes every year, multiplied again by the composite rate of the districts your parcel sits in. This rules file collapses all three into one constant, which is a rough estimate and is labelled as one. Read the dollar figure as an order of magnitude, not as a bill.

The assessment level used to convert market value to assessed value — 10.0% — rests only on secondary summaries. The Cook County Classification Ordinance could not be reached from any official host, and until the ordinance itself is read the value stays flagged. It scales every Cook dollar figure, so if it is wrong they are all wrong by the same proportion.

3 of the 3 sources listed below are still marked awaiting primary-source verification: Cook County Assessor's Office — Appeals; Cook County Board of Review — Residential Appeals; Illinois Property Tax Appeal Board (PTAB). A citation that has not been opened is treated as an open item even where the fact it supports is confirmed somewhere else. The full register of what is unresolved across the site, and what would close each item, sits behind the sources page; every correction to this county's ruleset is dated in the changelog.

None of this is legal or tax advice, and nothing here predicts an outcome. A board that hears your appeal weighs condition, renovations and location factors that this site does not model at all. Confirm your own deadline, your own fee and your own filing method with the Cook County Assessor's Office, then the Cook County Board of Review before you rely on any of it.