You open a Cook County property-tax bill, see the amount due, and think: This is too high. That reaction is understandable. It also leaves out the question the Board of Review can decide.
Quick Answer
The Board’s filing instructions name the complaint Property Over-Assessed. That question is whether the value assigned to the property is too high. Levies and tax rates are a different part of the bill. The amount due, standing alone, does not prove over-valuation.
The Board’s filing instructions give that question a name: **Property Over-Assessed**. The complaint asks whether the value assigned to your property is too high. It does not ask the Board to revisit every decision that eventually produced the bill.
That distinction can keep you from building an appeal around the wrong number.
A tax bill has two moving parts
The Illinois Property Tax Appeal Board answers “Why are my taxes so high?” with two components: the assessment of the property and the amount local taxing districts need to operate. An assessment appeal addresses the first component. Levies and tax rates arise from the second.
The Cook County Assessor does not set levies, rates, or bills. A lower assessment can affect a future bill, but an assessment change does not produce the same percentage change in taxes automatically. That is why the amount due, standing alone, does not prove over-valuation.
Your assessment notice and property record are the better starting points. Read the estimated market value. Check the listed characteristics. Then ask whether the evidence supports a different value.
Follow the Board’s example all the way through
The Cook County Board of Review uses a **$250,000 home** in its annual report to explain the residential calculation. This is the Board’s example, not your purchase price and not an estimate of what your home is worth.
Cook County residential property is assessed at 10% of estimated market value. In the Board’s illustration, the first calculation is:
**$250,000 × 10% = $25,000 assessed value**
The **$25,000** is the assessed value before the state equalization factor and exemptions. This is the part of the chain a Property Over-Assessed complaint seeks to change.
Next comes equalization. The Illinois Department of Revenue announced a final Cook County equalization factor of **3.0300** for **tax year 2025** on June 18, 2026. The final tax year 2024 factor was **3.0355**. Applying the tax year 2025 factor to the Board’s example produces:
**$25,000 × 3.0300 = $75,750 equalized assessed value**
The **$75,750** is EAV before exemptions. It is not a tax bill, a predicted savings amount, or a Tax Year 2026 multiplier. The factor equalizes county assessments to the statutory level; it is not a local tax rate.
Now consider the Homeowner Exemption. In Cook County, it can reduce EAV by up to **$10,000**. If the property in the Board’s example qualified for the full reduction, the calculation would be:
**$75,750 − $10,000 = $65,750 EAV after the exemption**
The **$65,750** still is not the amount on a check. It is the remaining EAV under that assumption. The exemption depends on eligibility and the applicable amount, and the $10,000 figure is a cap rather than an automatic reduction for every parcel. A local tax rate would be applied after exemptions to calculate the bill. Because no local rate belongs to this illustration, the math should stop at **$65,750** rather than inventing a bill or a savings claim.
Two different 10% figures can cause confusion
The residential assessment level of 10% is part of Cook County’s classification math. The Assessor also uses **10 percent** in a separate rule of thumb for deciding whether an appeal may be worthwhile.
The Assessor says that if the property characteristics are correct and the estimated market value is within 10 percent of what you believe the home is worth, an appeal is unlikely to change the assessed value enough to significantly affect the bill. If the characteristics are wrong, or if the estimated market value is significantly more than what the home could sell for in the current market, the Assessor says you should file an appeal.
This screening question brings the analysis back to the property. A recent arm’s-length closing may be useful evidence against the Assessor’s estimated market value. It does not turn the Board’s **$250,000** illustration into your purchase-price formula. A deed, contract, transfer declaration, appraisal, or well-supported comparable sale can help establish value; the amount due on the tax bill cannot do that work by itself.
Comparable evidence needs names, numbers, and a reason
Good comparable evidence is more than a screenshot of nearby houses. The properties should be meaningfully similar to yours. Age, square footage, class, construction, condition, and location can all affect whether a comparison deserves weight.
For an appeal filed with the **Cook County Assessor**, the Official 2026 Appeal Rules require at least **3 comparable properties**, recommend at least **5**, and require the **PIN for every comparable**. Those are Assessor rules, so do not mistake them for a separate Board filing standard. They are still a useful discipline: each comparison should be identifiable and tied to the claim you are making.
At the Board, the commissioners say their work is rooted in the evidence presented. Depending on the property and argument, that evidence may include an appraisal, comparable evidence, leases, rent rolls, Schedule E or income-and-expense statements, and demolition evidence. For a homeowner making a market-value or uniformity case, the practical question is simple: does this material show that the proposed assessment is fair and supported, or does it show a specific reason the value should be lower?
The appeal clock and payment clock keep running
If you are in Group 2 (Berwyn, Cicero, Elk Grove, Lakeview, Maine, or Palos), the window closes **Tuesday, September 29, 2026**. The Tax Year 2025 second installment is still due **Thursday, October 1, 2026**, even when an assessment complaint is pending. Board instructions say its decision is reflected in the following year’s tax bill.
So begin with the complaint the Board can hear. “My bill is high” explains why you looked. **Property Over-Assessed**, supported by evidence about the property’s characteristics and value, explains what you want the Board to decide.
If you need a starting point, Look up your PIN to review whether the assessment appears worth investigating before you pay anyone. County officials decide assessments and appeal outcomes.
Sources
- Cook County Board of Review, How to File an Appeal Online
- Cook County Board of Review, Tax Year 2024 Annual Report
- Illinois Property Tax Appeal Board, FAQ
- Cook County Assessor, Official 2026 Appeal Rules
- Illinois Department of Revenue, tax year 2025 Cook County final multiplier
- Censum FAQ
Sources accessed 2026-09-02.
FAQ
What does Property Over-Assessed mean?
It is the Board of Review complaint type for over-valuation of the assessment. The Illinois Department of Revenue says you appeal assessed value, not the tax bill or the tax rate. Once the bill arrives, it is generally too late to appeal that year’s assessment.
Is the Board’s $250,000 home my house?
No. It is the Board’s illustration: $250,000 times 10% is $25,000 assessed value, times the tax year 2025 factor 3.0300 is $75,750 EAV, and $65,750 after the full $10,000 Homeowner cap. No local rate is sourced, so there is no dollar bill or savings claim in that example.
How many comparables do I need?
For an Assessor filing, the Official 2026 Appeal Rules require at least 3 comparable properties, recommend 5, and require a PIN on every comparable. Those are Assessor rules, not a separate Board filing standard. They are still useful discipline.
Does Censum file the appeal for me?
No. Censum LLC is a data and analytics company, not a law firm and not a tax advisor. You file your own appeal.
Next step
Look up your PIN, then decide whether the evidence goes to characteristics and value. If you are in Group 2, the Board window closes Tuesday, September 29, 2026. Pay the October 1 installment anyway.
Censum LLC is a data and analytics company, not a law firm and not a tax advisor. You file your own appeal. Censum is independent and is not affiliated with Cook County or any government agency.