Illinois Commercial Property Tax Shock: How to Respond

 Posted on December 07, 2025 in Commercial Real Estate

Owners of commercial real estate in Illinois are experiencing one of the largest tax spikes in decades. Recent reassessments, particularly in Cook, DuPage, and Kane Counties, have sent commercial property values soaring – sometimes as much as 30 to 100 percent higher than in prior years. Landlords, developers, and investors are experiencing cash flow strain, escalating common-area maintenance (CAM) charges, and tenant disputes over tax pass-throughs.

Many of these assessment increases are based on aggressive income assumptions and outdated market comparables.  Barring a strategic appeal, these numbers can become locked in for years, raising both operating expenses and legal exposure with tenants. A highly skilled DuPage County, IL commercial real estate attorney can help you understand your rights and guide you through the appeal process.  

Why Are the 2024-2025 Illinois Commercial Reassessments So High?

There are several reasons why the commercial reassessments across Illinois are considerably higher than in past years. Assessors are adjusting values based on more recent and often inflated commercial real estate (CRE) sales post-pandemic.

There has also been a significant rise in replacement cost valuations on commercial properties. Inflation in construction materials, labor, and insurance has substantially increased the assessed value of many commercial properties. Assessors are relying more heavily on higher market rents and assumptions of lower vacancies, yet there are significant market inconsistencies across warehouses, flex spaces, and older office buildings.

How Will These Commercial Property Reassessments Affect Owners?

Owners may see massive jumps in property tax bills with little or no warning. Lenders are likely to require higher escrow requirements, and as the Net Operating Income (NOI) decreases, the valuation is lowered. The increases in commercial property reassessments can result in loan covenant pressures, including debt-service coverage ratios and jeopardized loan-to-value (LTV) requirements. These unexpected increases in property taxes on commercial properties are likely to result in landlord-tenant friction, and the landlords will almost certainly pass some or all of the extra costs to the tenants.

What Are the Best Strategies for Appealing an Illinois Commercial Property Assessment?

A successful tax appeal reduces the valuation, therefore the taxes assessed on the commercial property. Some of the best appeal strategies include:

Review the Assessor’s Data For Any Errors

Assessors are human and often make errors based on erroneous assumptions. Common errors include incorrect square footage, misidentified usage type, outdated condition ratings, incorrect vacancy assumptions, and wrong building classification.

Conduct a Comparable Property Analysis

Evidence related to similar properties with lower valuations should be gathered by the owner to present. Outdated or inaccurate rent rolls used by the assessor can be corrected to show the actual numbers.

Use the Income-Approach Challenge

The owner of a commercial property can challenge assumed rental rates and inflated market rent estimates. The owners can also challenge unrealistic vacancy factors, incorrect expense loadings, and miscalculated cap rates.

Structural or Environmental Challenges

Documented deferred maintenance can often reduce the overall valuation, particularly in cases of outdated HVAC systems or deterioration of the roof. Environmental contamination requiring remediation can also be presented.

Professional Appraisals and Advocacy by A Commercial Real Estate Attorney

Commercial Real Estate attorneys can work alongside a certified appraiser to prepare vacancy comparables and USPAP-compliant appraisals. Along with expert affidavits, market condition reports, and income-approach worksheets, you may be able to have your assessment lowered.

What is the Process for Appealing a Commercial Property Assessment?

The process for appealing a commercial property assessment varies by county. In Cook County, the owner files with the Assessor, then the Board of Review, and potentially with the Illinois Property Tax Appeal Board (PTAB) or Circuit Court. The deadlines are short – usually 30 days per stage. In DuPage and Kane Counties, a direct appeal to the Board of Review is filed, and then filed with the Property Tax Appeal Board. Evidence documents are often required at the time of filing.  

Contact a Naperville, IL Commercial Real Estate Attorney

You may be able to significantly reduce your reassessed commercial tax bill through a well-prepared appeal with the assistance of a DuPage County, IL real estate lawyer from The McCormick Law Firm, LLC. Attorney McCormick makes things easy to understand and offers discounts for military, veterans, and first responders. Call 630-517-8570 to schedule your free consultation.