How to Appeal Your Illinois Property Tax Assessment: 2026 Guide

If your Illinois property tax bill feels too high — and for many South Suburbs homeowners, it does — you may have the legal right to reduce it through a formal appeal. Illinois property tax assessments are not permanent, and the state’s multi-stage appeal system gives every homeowner a legitimate opportunity to challenge an excessive assessment and lower their annual tax bill. This 2026 guide walks you through exactly how to appeal your Illinois property tax assessment, from understanding how assessments work to filing with the Board of Review and, if necessary, the Property Tax Appeal Board (PTAB).

How Illinois Property Tax Assessments Work

Before appealing, it helps to understand what you’re actually appealing. In Illinois, your property tax bill is not calculated directly from your home’s market value. Instead, it follows a multi-step process:

• Market value: The assessor estimates what your property would sell for in an arm’s-length transaction
• Assessed value (AV): By law, Illinois residential property is assessed at 33.33% of market value (Cook County uses a different system — see below)
• Equalized assessed value (EAV): The assessed value multiplied by the state equalization factor (the “multiplier”), which the Illinois Department of Revenue sets annually to equalize assessment levels across counties
• Taxable EAV: Your EAV minus any exemptions you qualify for (homeowner exemption, senior exemption, etc.)
• Tax bill: Your taxable EAV multiplied by the combined tax rate of all taxing bodies (school district, municipality, county, park district, library, etc.)

When you appeal your assessment, you are arguing that the assessor’s estimate of your property’s market value is too high — which cascades down through the formula to reduce your final tax bill.

Cook County vs. Will County: Different Assessment Systems

Cook County

Cook County (which includes Oak Lawn, Evergreen Park, Burbank, Tinley Park, Alsip, Blue Island, Calumet City, and many other South Suburbs) operates on a triennial reassessment cycle. Cook County is divided into three geographic assessment districts — north suburbs, south suburbs/city of Chicago south, and north/northwest city — and each district is reassessed every three years on a rotating basis. This means your property is formally reassessed by the Cook County Assessor once every three years, though you can appeal after every reassessment notice.

In Cook County, residential property is classified and assessed at 10% of market value (rather than the statewide 33.33%), with the state equalization multiplier applied to bring the effective rate toward the statewide level. The Cook County Assessor’s office sends reassessment notices by mail when your township is reassessed — watch for this notice, as it triggers your appeal window.

Will County

Will County (which includes Frankfort, Mokena, New Lenox, Homer Glen, Romeoville, and other South Suburbs) follows the standard Illinois residential assessment rate of 33.33% of market value, with annual reassessment cycles. Will County homeowners receive a notice of assessment from their township assessor, which triggers the appeal window. Will County’s overall property tax burden is lower than Cook County’s, but appeals are still possible and sometimes warranted when assessments outpace market values.

Step 1: Check Your Exemptions First

Before filing a formal appeal, confirm you are receiving every exemption you are entitled to. Missing exemptions are the most common and easily corrected reason for excessive tax bills:

• General Homestead Exemption (Homeowner Exemption): Reduces EAV by $10,000 for owner-occupied residences. Applies in Cook County and all Illinois counties. Must be applied for in your first year of ownership — it does not apply automatically after purchase.
• Senior Citizens Homestead Exemption: Additional $8,000 EAV reduction for homeowners 65 or older who own and occupy their property. Must be applied for annually in some counties.
• Senior Citizens Assessment Freeze (Senior Freeze): For income-qualifying seniors (household income under $65,000 in Cook County), this freezes your EAV at a base year value — preventing further increases even if market values rise. This is one of the most powerful exemptions available and is significantly underutilized.
• Persons with Disabilities Exemption: Additional $2,000 EAV reduction for qualifying disabled homeowners.
• Veterans with Disabilities Exemption: Ranging from partial to complete exemptions for qualifying veterans depending on disability rating.
• Returning Veterans Exemption: One-time $5,000 EAV reduction in the year a qualifying veteran returns from active duty.

To check your current exemptions in Cook County, visit the Cook County Assessor’s website (cookcountyassessor.com) and search by PIN. In Will County, contact your township assessor directly. If you’re missing exemptions, file the appropriate application immediately — exemptions can sometimes be applied retroactively for prior years if you can demonstrate you were eligible.

Step 2: Determine If Your Assessment Is Accurate

Your assessment is your target. In Cook County, your property’s market value is implied by dividing your assessed value by 10% (the county’s assessment level). If your assessed value is $35,000, the assessor is saying your home is worth $350,000. Is that accurate? Research recent comparable sales:

• Look up recent sales of similar homes in your neighborhood — same street type, similar square footage, similar bedroom/bathroom count, similar condition — within the past 12–18 months
• Check Zillow, Redfin, and Realtor.com for sold prices of comparable properties
• Request a market analysis from a local real estate agent — they can pull MLS data with more precision than public sites
• If your implied market value exceeds recent comparable sales by 10% or more, you likely have a strong basis for appeal

Also look for factual errors in the assessor’s property record: incorrect square footage, wrong number of bedrooms or bathrooms, listing a garage that doesn’t exist (or vice versa), noting an addition that was never built. Factual errors are the strongest basis for assessment reduction and are corrected more readily than valuation disputes.

Step 3: File with Your County Board of Review

Cook County Board of Review

In Cook County, the appeal process begins with the Cook County Board of Review (CCBOR). The appeal window opens when your township’s reassessment notices are mailed (township-specific dates, published on the CCBOR website) and typically closes 30 days later. Missing this window means waiting until the next reassessment cycle — up to three years. Key steps:

• File online at the CCBOR website (cookcountyboardofreview.com) — you don’t need an attorney to file a Board of Review appeal
• Submit comparable sales evidence: Typically 3–5 comparable sales from the prior 12–18 months that support a lower market value. The CCBOR provides form worksheets.
• Include any factual error evidence: Photos, permits, or appraisals that contradict the assessor’s property data
• The hearing process: Most residential appeals are decided on the written submission without a personal appearance. You may be contacted for additional information.
• Decision timeline: Board of Review decisions typically arrive 3–6 months after filing. If successful, your reduced assessment applies to the current tax year.

Will County Board of Review

Will County homeowners appeal first to the Will County Board of Review. The process is similar to Cook County — file a complaint with comparable sales evidence during the open appeal window for your township (typically 30 days after assessment notices are mailed). Will County’s Board of Review is generally considered more accessible for self-represented homeowners, and the success rate for well-supported appeals is meaningful.

Step 4: If the Board of Review Doesn’t Give Full Relief — PTAB

If the Board of Review reduces your assessment but not enough — or not at all — you have the right to appeal further to the Illinois Property Tax Appeal Board (PTAB). PTAB is a state agency that hears property tax appeals de novo (fresh review, not just reviewing what the Board of Review did). Key PTAB facts:

• Filing deadline: 30 days from the date of the Board of Review’s final decision
• Evidence standard: PTAB expects more formal evidence packages — typically a certified appraisal or a detailed comparable sales grid prepared by a licensed appraiser or qualified attorney
• Timeline: PTAB proceedings can take 1–3 years to resolve, particularly in Cook County where the docket is large
• Retroactive savings: If PTAB rules in your favor, the reduction applies to the tax year being appealed — often resulting in a tax refund for overpaid prior bills
• Attorney representation: For PTAB appeals, most homeowners benefit from professional representation — a property tax attorney or certified appraisal professional can significantly improve outcomes on contested cases

DIY vs. Hiring a Property Tax Attorney

For Board of Review appeals, most South Suburbs homeowners can successfully file on their own — particularly if they have clear comparable sales evidence or a factual error to document. The process is designed to be accessible without legal representation, and the Cook County Board of Review’s online portal is reasonably user-friendly.

For PTAB appeals, professional representation is generally worth the cost. Property tax attorneys in Illinois typically work on contingency — they charge a percentage of the first year’s savings (often 30–50% of the tax savings for the appealed year), with no fee if they’re unsuccessful. On a Cook County home with a $7,500 annual tax bill, a successful 15% reduction saves $1,125 per year — and the attorney takes a share of the first year’s savings only. In subsequent years, you keep 100% of the ongoing savings.

How Much Can You Save by Appealing?

Successful Cook County Board of Review appeals in the south and southwest suburbs have historically reduced assessments by 10–25% in cases with strong comparable sales evidence. On a home with a $7,500 annual tax bill, a 15% reduction saves $1,125 per year — and if the assessment stays reduced for the full three-year triennial period, the cumulative savings are $3,375 before the next reassessment cycle. For PTAB appeals on higher-assessed commercial or residential properties, annual savings can reach $5,000–$20,000+ for successful outcomes.

Property Tax Appeal Calendar: Key Dates to Know

• Cook County: Township-specific reassessment and appeal windows published annually at cookcountyboardofreview.com. Missing your township’s window means waiting for the next cycle.
• Will County: Assessment notices mailed spring/summer, with appeal windows typically 30 days. Contact your township assessor for specific dates.
• PTAB: 30 days from Board of Review decision to file. No extensions.
• Exemption applications: Annual deadlines vary — Cook County homeowner exemption applications typically due by end of calendar year for the following tax year. File early.

Working with Krembo Group: We Know the South Suburbs Tax Landscape

When you work with Krembo Group to buy a home in the South Suburbs, part of our value is helping you understand the property tax picture — not just the purchase price. We explain which exemptions to apply for immediately after closing, flag properties that appear over-assessed relative to comparable sales, and connect you with trusted property tax professionals for ongoing appeal support. Contact us to start your South Suburbs home search with a team that thinks about your total cost of ownership, not just the listing price.

Frequently Asked Questions: Illinois Property Tax Appeals

How do I appeal my property taxes in Illinois?

File a complaint with your county’s Board of Review during the open appeal window for your township — typically 30 days after reassessment notices are mailed. In Cook County, file online at cookcountyboardofreview.com. Submit comparable sales evidence showing your property’s market value is lower than the assessor’s implied value. If unsatisfied with the Board of Review result, you may escalate to the Illinois Property Tax Appeal Board (PTAB) within 30 days of the Board’s decision.

How often are Illinois property taxes reassessed?

Cook County residential properties are reassessed on a triennial (every 3 years) cycle, with different townships reassessed in rotating years. Will County and most other Illinois counties conduct annual assessments. Check your county assessor’s website for your township’s specific reassessment schedule.

What evidence do I need to appeal my Illinois property tax assessment?

For a Board of Review appeal, the most effective evidence is a grid of 3–5 comparable sales of similar homes in your neighborhood from the prior 12–18 months, showing that the market value implied by your assessment exceeds what similar homes actually sold for. Factual errors (wrong square footage, non-existent improvements) supported by photos or permits are also strong evidence. For PTAB appeals, a certified independent appraisal is typically required for the strongest case.

How long does a Cook County property tax appeal take?

Board of Review appeals in Cook County typically take 3–6 months from filing to decision. PTAB appeals can take 1–3 years, especially in Cook County where the docket is large. However, successful appeals retroactively apply to the tax year being contested, meaning refunds or credits for overpaid taxes are possible even after extended waits.

Can I appeal my property taxes every year in Illinois?

In Cook County, formal Board of Review appeals can only be filed in the year your township is reassessed (every three years). In Will County and most other Illinois counties, you can file a Board of Review appeal every year during the annual appeal window. PTAB appeals can follow any Board of Review decision. Additionally, exemption applications can be filed annually and are separate from formal assessment appeals.

Do I need a lawyer to appeal my Illinois property taxes?

No — Board of Review appeals in Cook and Will Counties are designed to be filed without attorney representation, and many homeowners successfully appeal on their own with well-prepared comparable sales evidence. For PTAB appeals, professional representation (a property tax attorney or qualified appraiser) significantly improves success rates and is typically taken on contingency — no fee unless they succeed in reducing your assessment.