Cook County Property Tax Appeal: How to Do It Yourself
If your Cook County assessment notice shows a value that feels too high, you can appeal it — free, on your own, without paying a company a cut of your savings. Cook County runs one of the more layered appeal systems in the country, with two separate levels before you ever reach a formal hearing board. Most homeowners can work through it in a few hours if they know where to start. This is general information, not legal or tax advice. Rules, deadlines, and procedures in Cook County can change — always verify current details with the Cook County Assessor's Office or the Board of Review before you file.
The Appeal Deadline — Confirm It the Day Your Notice Arrives
Cook County reassesses on a triennial cycle; each township has its own complaint window. Missing your window means no appeal for that tax year — no grace period. Check the current schedule at cookcountyassessor.com the day your notice arrives.
Grounds for Appeal: What You Can Actually Argue
Illinois law recognizes two main grounds that apply to most residential homeowners in Cook County.
- Overvaluation: the assessed value exceeds what comparable recent sales support as your property's market value.
- Lack of uniformity (equity): your property is assessed at a higher ratio to market value than comparable nearby properties, even if the absolute number seems plausible.
You can raise both grounds in the same complaint — and most homeowners do, since gathering comparable sales covers both arguments simultaneously. Cook County's Assessor portal also displays comparable properties the Assessor used, which can reveal inconsistencies worth flagging directly.
How to File: Assessor First, Then Board of Review
The Assessor's Office accepts complaints online through its appeal portal at cookcountyassessor.com during your township's open window. You will need your Property Index Number/PIN, your opinion of the correct value, your grounds, and your supporting evidence — unlike some other Illinois counties, Cook County's Assessor level expects you to submit evidence at the time of filing, not just at a hearing. Upload comparable sales, any independent appraisal you have, and photos documenting condition issues.
If the Assessor does not reduce your value enough — or at all — you can file a separate complaint with the Cook County Board of Review. The Board has its own filing window (typically after the Assessor's level closes for your township) and its own online portal. State your grounds and provide your evidence again; the Board schedules an informal or formal hearing where you present your case to an independent panel. Confirm current Board of Review deadlines and procedures at cookcountyboardofreview.com — do not assume the Assessor-level and Board-level windows overlap.
Evidence That Moves the Board of Review
Print everything and organize it clearly — a panel that sees a tidy packet treats you as a prepared, credible filer. The most useful evidence for a Cook County residential appeal:
- Three to five comparable sales from the past 12 months: nearby homes with similar size, age, and condition that sold below what your assessed value implies.
- Assessed values per square foot for neighboring properties from the Cook County Assessor's public records portal — the core data for a uniformity argument.
- Photos and repair estimates for condition issues the Assessor may not have on file — roof damage, foundation problems, water intrusion. Interior condition evidence can shift the assessed number.
- A recent independent appraisal from a refinance or purchase, if the appraised value came in below your assessment — carries real weight as a licensed professional's market-value opinion.
A reduction is not guaranteed — it depends on how well your evidence aligns with the Board's standards and the comparable data on record. Strong, recent sales from within your neighborhood are the most reliable path to a lower assessed value.
DIY vs. Hiring an Appeal Company
Appeal firms charge a contingency fee — a cut of first-year savings. For a standard single-family home with clear comps, the DIY path typically produces the same outcome at no cost. Cook County's two-level system adds administrative steps, but both portals are built for homeowners filing without an attorney. Consider a firm only for complex properties or when you cannot spare the time — ask about fees and what happens if the appeal fails before signing.
What Actually Happens to Cook County Appeals: The County's Own Numbers
Cook County publishes the outcome of every appeal as open data. The figures below are calculated directly from two of those datasets — the Assessor's Appeals file and the Board of Review's Appeal Decision History — so they describe what happened to real cases, not what anyone estimates. The two stages behave very differently, and that difference is the single most useful thing to know before you file.
| Tax year | Assessor: appeals decided | Assessor: share reduced | Board of Review: residential appeals | Board of Review: share reduced |
|---|---|---|---|---|
| 2024 | 440,743 | 21.2% | 490,231 | 39.9% |
| 2023 | 243,416 | 21.4% | 330,843 | 34.1% |
| 2022 | 302,316 | 24.9% | 392,855 | 28.5% |
Read the two columns against each other. In 2024 the Assessor reduced 21.2% of the appeals it decided. The Board of Review reduced 39.9% of residential appeals — close to twice the rate. The Board is the second stage, it sees the case after the Assessor has already declined to move, and it still cuts the assessment in roughly four cases out of ten. That is the practical argument for not stopping after an Assessor denial: the stage with the better odds comes after it. Across the Assessor's 440,743 decided appeals in 2024 the total assessed value under appeal fell 6.8%.
Can an Appeal Make Your Assessment Go Up?
This is the fear that stops most people from filing, and in Cook County it can be answered with a count rather than a reassurance. Of 490,231 residential appeals the Board of Review decided for tax year 2024, the assessment was increased in 90. That is 0.018% of cases — roughly 5,447 to one against. The pattern holds across years: 125 increases in 330,843 residential appeals for 2023, 318 in 392,855 for 2022, and 63 in 447,780 for 2025.
The share of appeals that succeed has also been rising at the Board: 28.5% of residential appeals reduced for 2022, 34.1% for 2023, 39.9% for 2024 and 42.3% for 2025. Whatever is driving that trend, the direction has been consistent for four assessment years.
Reduction Rates by Township, Tax Year 2024
Cook County reassesses on a three-year township cycle and appeal windows open township by township, so your neighbours a few miles away may be on a different schedule entirely. The table lists every township with at least 5,000 decided appeals at the Assessor stage in 2024, with the share that ended in a reduction.
| Township | Appeals decided | Share reduced |
|---|---|---|
| Lake View | 66,785 | 30.5% |
| North Chicago | 60,081 | 16.4% |
| West Chicago | 53,452 | 22.1% |
| Jefferson | 49,575 | 30.6% |
| South Chicago | 48,041 | 12.3% |
| Lake | 18,145 | 28.0% |
| Hyde Park | 15,729 | 25.0% |
| Rogers Park | 11,584 | 30.5% |
| Wheeling | 8,527 | 11.9% |
| Worth | 8,256 | 17.3% |
| Thornton | 7,435 | 21.2% |
| Lyons | 7,132 | 18.2% |
| Orland | 6,461 | 15.7% |
| Proviso | 6,114 | 17.6% |
| Palatine | 5,789 | 7.6% |
| Niles | 5,613 | 15.2% |
Why the spread matters. Among these townships the reduction rate at the Assessor stage ranged from 7.6% in Palatine to 30.6% in Jefferson — a gap of 23.0 percentage points in the same county, same year, same rules. A low rate in your township is not a reason to skip filing; it is a reason to expect the Assessor stage to be the harder one and to plan on continuing to the Board of Review, where the rates above apply.
Cook County Appeals: Questions the Data Answers
How many appeals does Cook County actually decide each year?
More than most people assume. The Assessor decided 440,743 appeals for tax year 2024 and the Board of Review decided 490,231 residential appeals. Filing is routine here, not exceptional.
Do I have to appeal to the Assessor before the Board of Review?
No. The two are separate bodies with separate windows, and you can go to the Board of Review whether or not you filed with the Assessor first. Most homeowners use both, because the Assessor stage costs nothing and an early reduction ends the matter.
Which stage gives me the better chance?
On the published outcomes, the Board of Review. For tax year 2024 the Assessor reduced 21.2% of decided appeals; the Board reduced 39.9% of residential appeals, and its rate rose again to 42.3% for 2025.
Is there any filing fee at either stage?
No. Both the Assessor and the Board of Review accept appeals at no charge, online or on paper. A cost only arises if you engage an attorney or appeal firm, which normally works for a share of the first-year saving.
What grounds do residential appeals actually use?
Overvaluation — the argument that the assessed value is higher than it should be, usually shown through comparable properties assessed lower. Every residential appeal the Board of Review decided for tax year 2024 was recorded under that heading.
Why does my township have a different deadline than the next one?
Cook County reassesses one third of the county each year on a township cycle, and appeal windows follow the reassessment. The window for your township is published by township, and it is short — usually around 30 days from the date notices go out.
Sources. All figures on this page are calculated from Cook County open data: the Cook County Assessor's Appeals dataset and the Cook County Board of Review's Appeal Decision History dataset, both published on the Cook County Open Data portal. Shares are computed by comparing the value before and after each decision, case by case, for the tax years shown. Only aggregate counts are reported here.