The case for appealing
Why uniformity appeals work in Cook County
Cook County has one of the most thoroughly documented assessment accuracy problems in the country. The data shows it. The research confirms it. That's why uniformity appeals succeed here at high rates.
The assessment accuracy problem
A landmark 2017 investigation by the Chicago Tribune found that Cook County's assessment system was deeply regressive — lower-value homes were being taxed at rates far higher than more expensive homes, often in the same neighborhood. The University of Chicago's Center for Municipal Finance published follow-up research confirming the pattern using CCAO's own data.
The problem isn't fraud — it's the inherent difficulty of mass appraisal at scale. When the CCAO estimates values for 1.8 million parcels using statistical models, individual properties end up over- or under-assessed by significant margins. The system flags the overall accuracy rate as acceptable while hiding wide variation at the individual property level.
What the data shows
of Cook County residential properties that appeal their assessment receive a reduction, according to Board of Review historical data.
in assessment reductions granted annually by the Cook County Board of Review — money that would otherwise have been collected as excess taxes.
of eligible homeowners actually file appeals, according to CCAO records — meaning the vast majority of over-assessed properties never get corrected.
Why uniformity is the right argument
There are two ways to appeal a Cook County property tax assessment:
Overvaluation appeal
Argue that your home's market value is lower than the CCAO estimates. Requires a recent arm's-length sale or a professional appraisal. Appraisals typically cost $300–$600. Works best if you recently purchased below the CCAO's estimated value.
Uniformity appeal ← this is what we do
Argue that similar properties nearby are assessed at a lower rate per square foot. No appraisal needed. Uses public CCAO data. Works regardless of your home's market value — even if the CCAO's market value estimate is accurate. The legal standard is equal treatment, not absolute accuracy.
For most homeowners, the uniformity argument is both stronger and cheaper. It doesn't require you to prove anything about what your home is “really” worth — only that your neighbors are paying less per square foot for similar homes.
The legal basis
The uniformity requirement is codified in the Illinois Property Tax Code (35 ILCS 200/9-145) and the Illinois Constitution (Article IX, Section 4), which requires that all real property be taxed uniformly. Illinois courts have consistently held that a taxpayer can obtain an assessment reduction by showing that comparable properties are assessed at a lower level — even if the taxpayer's own assessment accurately reflects market value.
In other words: fairness is a separate legal standard from accuracy. You can be accurately assessed and still win a uniformity appeal.
Why most homeowners don't appeal
The barriers are informational, not legal. Most homeowners don't know:
- ·That they have the right to appeal every year the township is in reassessment
- ·That the filing process is online and free at the Board of Review
- ·What their comparable properties are and how to find them
- ·That a uniformity argument requires no appraisal — just public data
TaxedTooMuch closes those gaps. We do the data work. You file the form.
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