Cook County Value

How to Appeal Your Cook County Property Tax Assessment

Cook County has the highest property taxes in the nation, with a median annual bill over $6,000. The Assessor reassesses properties on a triennial (3-year) cycle, and many homes are over-assessed. Filing an appeal is free at the Assessor level and can save you hundreds or thousands of dollars each year.

How Cook County Assessment Works

Unlike most states, Cook County uses a 10% assessment ratio for residential properties. The Assessor estimates your home's Fair Market Value, then multiplies by 10% to get the Assessed Value. An Equalization Factor (set by the Illinois Department of Revenue) is then applied to calculate your Equalized Assessed Value (EAV), which is what your tax bill is based on.

When you appeal, you're challenging the Assessor's estimate of your home's Fair Market Value. A lower market value means a lower assessed value, which means a lower tax bill.

When Is the Deadline?

Cook County uses rolling township deadlines. The county is divided into townships that are reassessed on a rotating 3-year cycle: City of Chicago, North Suburbs, and South/West Suburbs. Your township's appeal window opens when reassessment notices are mailed and typically stays open for 30 days.

Check the Assessor's website at cookcountyassessor.com for your township's specific deadline. Appeals are accepted year-round as different townships cycle through reassessment.

For 2026, we have loaded current assessment values for these townships:

Two Levels of Appeal

Cook County offers two levels of appeal, and you can use both:

  1. Assessor's Office: File first with the Cook County Assessor. This is free and entirely online. Many appeals are resolved at this level.
  2. Board of Review: If you're unsatisfied with the Assessor's decision (or want a second chance), file with the Cook County Board of Review. There is no filing fee for residential properties.

You can file at both levels each reassessment cycle — and you should. Even if the Assessor reduces your value, the Board of Review may reduce it further.

Step 1: Review Your Assessment

Look up your property on Cook County Value to see your assessed value, comparable properties, and potential savings. Check the Assessor's records for accuracy — verify your square footage, year built, number of rooms, and property condition. Data errors are common and can inflate your assessment.

Step 2: Gather Evidence

The two most effective appeal strategies in Cook County:

  • Comparable properties (equity): Show that similar homes in your area have lower assessed values per square foot. This is the most common and effective approach. Find 3-5 comparable homes with lower valuations.
  • Recent sales: Show that recent sales of similar homes indicate your property is worth less than the Assessor's Fair Market Value estimate. Bring sale dates, addresses, and prices from the last 1-2 years.

Cook County Value generates both types of evidence automatically using the Assessor's own data and public sales records.

Step 3: File Your Appeal Online

The Cook County Assessor accepts appeals online:

  1. Go to cookcountyassessor.com/online-appeals
  2. Search for your property using your 14-digit PIN
  3. Select your reason for appeal (comparable properties, recent sales, or both)
  4. Upload your evidence (comparable property list, sales data, photos)
  5. Submit before your township's deadline

Tips for Cook County Appeals

  • Appeal at both levels — Assessor first, then Board of Review
  • Focus on 3-5 strong comparable properties with lower $/sqft values
  • Check for data errors — wrong square footage is the easiest win
  • Document any condition issues with dated photos
  • You can appeal every reassessment cycle (every 3 years for your township)
  • Even small reductions compound — a $20,000 reduction saves $400+ annually
  • The Assessor's phone number is 312-443-7550

Sources and evidence for Cook County

Prepared by Cook County Value. Filing resources checked September 17, 2026.

Start with the Cook County Assessor's Office property record and your current notice. Our property pages organize imported public assessment records and available comparable evidence. Check the tax year and data dates shown on each page: a prior-year record is useful history, but does not establish the value on a new notice.

Comparable homes are candidates for review. Verify their size, age, condition, location, and sale details before using them. Value per square foot helps screen candidates; it does not account for every difference. Estimated savings depend on the final assessment, exemptions, assessment limits, and applicable tax rates.

Cook County filing windows and value types

Assessor deadlines vary by township and are separate from Board of Review deadlines. Confirm your township’s current filing window on the Assessor calendar and check the Board of Review separately.

Residential assessed value is generally 10% of estimated fair market value. Our comparisons display full market values; use matching value types and tax years when checking the official record. Exemptions and the eventual tax rate affect the bill separately.

Check the source before filing

Cook County Value is an independent research tool. Verify the current procedure with Cook County Assessor's Office, save a copy of your evidence, and retain your filing confirmation. The appraisal authority or review board decides the outcome.

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