Illinois Property Tax Appeal Guide | Property Tax Edge
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Illinois

Midwest · 102 counties

Complete property tax appeal guide for Illinois homeowners — rates, deadlines, exemptions, and step-by-step appeal instructions.

Illinois Property Tax Appeal BoardComplex to Appeal
1.88%
Effective Tax Rate
Rank #1 nationally
33.33%
Assessment Ratio
33.33% of market value (Cook County varies)
$263,300
Median Home Value
latest Census/ACS estimate
$5,298
Median Annual Tax
Per year
1

Tied with New Jersey for the highest effective tax rate in the US on the Tax Foundation measure

2

Cook County uses a classification system with different ratios for residential vs. commercial

3

Triennial reassessment cycle — your township is reassessed every 3 years

Appeal Deadline

30 days from PUBLICATION of the assessment list outside Cook County; per-township dates in Cook

Outside Cook County the 30 days runs from publication of the assessment list (35 ILCS 200/16-55), not from the postmark on your notice — counting from the notice can file you late. In Cook County the deadline is set township by township and printed on the Board of Review notice; check the Assessor's township schedule.

Verified August 2026 against the official source · official source · always confirm the current date with your county

Understanding Illinois's Assessment Ratio

33.33%
33.33% of market value (Cook County varies)

Illinois uses a 33.33% assessment ratio, meaning your assessed value is set at 33.33% of your property's estimated market value.

To find your implied market value: Divide your assessed value by 0.3333.
Example: Assessed value of $87,757.89 ÷ 0.3333 = $263,300 implied market value

⚠ Common Mistake: Never compare your assessed value directly to comparable sale prices in Illinois. Always convert to implied market value first.

How to Appeal Your Property Tax in Illinois

1

Receive assessment notice from township assessor

2

File appeal with the County Board of Review within 30 days of PUBLICATION of the assessment list (Cook County uses per-township dates printed on your notice)

3

Attend Board hearing

4

Appeal to the Property Tax Appeal Board (PTAB) within 30 days of Board decision

5

Or file a tax objection complaint in Circuit Court

Appeal Body
County Board of Review → Property Tax Appeal Board (PTAB) → Circuit Court

Exemptions & Relief Programs

Homestead Exemption
General Homestead Exemption: $10,000 EAV reduction (Cook); $6,000 downstate
Senior / Disabled Exemption
Senior Citizens Homestead Exemption: $8,000 EAV reduction (Cook); $5,000 downstate

Key Statutes & Legal References

§
35 ILCS 200/9-145 (33.33% ratio)
§
Cook County Classification Ordinance (varies by class)
§
35 ILCS 200/16-55 (Board of Review appeal)
§
35 ILCS 200/16-160 (PTAB appeal)

Illinois Property Tax Code

Governing Code
Illinois Property Tax Code (35 ILCS 200)
Assessment Authority
Township/County Assessor
Appeal Board
Board of Review
Assessment Cycle
Triennial (Cook County); varies by county

Key Statutes

35 ILCS 200/9-145
Assessment Level
Establishes the 33.33% assessment level for all real property in Illinois.
35 ILCS 200/16-55
Board of Review Complaints
Establishes the process for filing complaints with the county Board of Review.
35 ILCS 200/16-160
Property Tax Appeal Board
Creates PTAB as the statewide administrative body for property tax appeals.
35 ILCS 200/15-175
General Homestead Exemption
Provides up to $10,000 reduction in equalized assessed value for owner-occupied homes.

Major Exemptions

General Homestead Exemption
Owner-occupied primary residence
$10,000 EAV reduction
Senior Homestead Exemption
Age 65+, owner-occupied
$8,000 EAV reduction
Senior Assessment Freeze
Age 65+, income ≤$75,000 (tax year 2026; $77,000 for 2027, $...
Frozen EAV
Official Code

Illinois Appeal Tools

Use these tools to build your appeal case for Illinois:

Over-Assessment Calculator
County Appeal Guides
Jurisdiction Intelligence
CAD Interactive Map
Sales Comparables Tool
Deadline Manager

Quick Illinois Calculator

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Assessment ratio: 33.33% · Rate: 1.88%

Quick Links

Over-Assessment Calculator
Find a Consultant
Deadline Manager
Community Forum
Complex to Appeal
Among the highest rates in the US; Cook County has a unique classification system; triennial reassessment creates backlogs

Taxing Authority

Township/County Assessor
Assessment Frequency
Triennial

Ready to Appeal Your Illinois Property Tax?

Use our free tools to calculate your potential savings, find a local consultant, and manage your appeal deadlines.

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Illinois's assessment ratio study

How closely Illinois assessors' values actually track real sale prices — and whether you can use that in an appeal.

Applied directly in appealsLatest study: 2024

Sales Ratio Study (Table 3, Illinois Property Tax Statistics); methodology in PTAX-1-E

The county's IDOR median level of assessment is the denominator in an Illinois lack-of-uniformity claim: at the Board of Review or PTAB, show the assessed value exceeds proven market value multiplied by the county's three-year median level — which in Cook County means roughly 10–11% residential, not 33 1/3%.

Official Illinois dataCompare all 50 states + DC

What's changing in Illinois

Enacted 2026 legislation and certified ballot measures. Reviewed August 2026 — always confirm with your county before relying on a change that hasn't taken effect yet.

EnactedPublic Act 104-0452 (SB 642)Action may be needed

Senior freeze income limit raised to $75,000

Raises the Low-Income Senior Citizens Assessment Freeze income limit to $75,000, then $77,000 for 2027 and $79,000 from 2028. The senior deferral programme limit rises on the same schedule. An annual PTAX-340 filing is still required — the freeze drops off if you miss it.

Effective: Tax year 2026 (payable 2027)tax.illinois.gov

Supplemental, Escape & Corrected Bills in Illinois

Illinois never sends a mid-year supplemental bill - new construction is prorated onto the next regular (arrears) bill. The bills to watch are omitted-property assessments, which can reach back 3 years and arrive as separate bills after notice and a hearing; certificates of error handle after-the-fact corrections and refunds.

Omitted Property Assessment

Assessor discovers property (land, improvements, or leaseholds) that escaped assessment; may assess for the current year and up to 3 prior years. Taxpayer is entitled to notice and an opportunity to be heard before the omitted assessment is finalized; good-faith purchaser and bona-fide-payment defenses limit back-billing.

Appeal window: Contest through the county Board of Review (complaint window varies - generally 30 days from the board's published notice for the township, or per the omitted-assessment hearing notice), then PTAB or circuit court (tax objection) within 30 days of the BOR decision.

Certificate of Error

Assessor (with Board of Review concurrence in Cook) acknowledges a mistake discovered after the rolls closed - wrong exemption, factual error, duplicate assessment, etc.; produces a corrected/refunded bill.

Appeal window: Taxpayer-initiated certificate-of-error requests generally may cover recent back years (e.g., 3 prior years for exemption-related errors under 35 ILCS 200/14-25); some certificates require court approval. Not a fixed day-count from a notice.

New improvement proration (on regular bill)

Improvements completed mid-year are assessed on a proportionate basis for the portion of the year they were habitable/occupied (35 ILCS 200/9-180) - but this appears on the NEXT regular bill, not a separate supplemental bill.

Appeal window: Normal annual appeal windows (township BOR filing periods; Cook County Assessor/BOR complaint windows).

Full details & sources →Got one of these bills? Track its deadline →
AI Evidence Packet · $49

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We prepare the evidence — you submit it. The $49 is charged when the packet is generated, not when an appeal succeeds. See a sample packet.

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Illinois property tax appeals — frequently asked questions

When is the property tax appeal deadline in Illinois?+

In Illinois, the appeal window is 30 days from PUBLICATION of the assessment list outside Cook County; per-township dates in Cook. Outside Cook County the 30 days runs from publication of the assessment list (35 ILCS 200/16-55), not from the postmark on your notice — counting from the notice can file you late. In Cook County the deadline is set township by township and printed on the Board of Review notice; check the Assessor's township schedule. Always confirm the exact date with your local township/county assessor or appeal board, as it can vary by county.

How do I appeal my property tax assessment in Illinois?+

The general process: 1) Receive assessment notice from township assessor; 2) File appeal with the County Board of Review within 30 days of PUBLICATION of the assessment list (Cook County uses per-township dates printed on your notice); 3) Attend Board hearing; 4) Appeal to the Property Tax Appeal Board (PTAB) within 30 days of Board decision; 5) Or file a tax objection complaint in Circuit Court. Appeals are heard by the County Board of Review → Property Tax Appeal Board (PTAB) → Circuit Court.

What is the average property tax rate in Illinois?+

Illinois's effective property tax rate is about 1.88% of value — roughly $5,298 per year on the state's median home value of $263,300. Assessments are made at 33.33% of market value (Cook County varies).

What exemptions can lower my property tax in Illinois?+

Common relief includes the homestead exemption (General Homestead Exemption: $10,000 EAV reduction (Cook); $6,000 downstate) and senior relief (Senior Citizens Homestead Exemption: $8,000 EAV reduction (Cook); $5,000 downstate). Eligibility and amounts vary — check with Illinois Property Tax Appeal Board.

Is it worth appealing my property taxes in Illinois?+

If your assessed value is higher than what your home would realistically sell for, an appeal can lower your bill — often for the life of the assessment. Use the free over-assessment calculator to estimate your potential savings before you file.