Commercial & Business Property
Illinois Commercial Property Tax Appeals
Office, retail, industrial, multifamily, and special-purpose buildings in Illinois are frequently over-assessed. Here's how commercial assessments work, the deadline to challenge yours, and what it takes to win.
How commercial is assessed
Illinois assesses commercial at 33.33% of market value in the collar/downstate counties. Cook County is different: commercial/industrial is assessed at a 25% level vs 10% for homes, then a state equalizer is applied.
Cook assesses commercial/industrial at ~25% (vs 10% residential); collar/downstate use 33.33% for all.
Burden of proof
The property owner (or their authorized agent) bears the burden of proving the assessment exceeds market value. The assessor's value is presumed correct until rebutted with credible evidence.
Key to a Illinois commercial appeal: Uniformity appeals + the equalization factor
Illinois is a uniformity state — a commercial appeal can win by showing your assessment-per-square-foot is higher than comparable properties, not just that market value is lower. Cook publishes comparables; collar counties use the DevNet portal. Windows are rolling by township.
Illinois Filing Deadline & Where to File
File With
County Board of Review (or CCAO in Cook County)
Deadline
30 days from publication date (Cook County has specific calendar)
Window Opens
After township assessments published (varies by township)
Typical Duration
3–12 months (Cook County can take 12+ months)
Cook County has its own system (CCAO). Reassessment is on a triennial cycle by township. Assessment level is 33.33% of market value (10% in Cook for residential).
⚠️ Deadlines vary by county/municipality in Illinois. Confirm the exact date for your property's jurisdiction before filing.
How commercial value is proven
Income-producing commercial property is usually valued by capitalizing net operating income (NOI ÷ market cap rate). The strongest appeals come with a clean rent roll, a trailing-12-month operating statement, current vacancy, and market cap-rate support. Where the property is owner-occupied or special-purpose, the cost and sales-comparison approaches carry more weight.
Evidence that wins a commercial appeal
- Current rent roll and a trailing-12-month operating statement
- Actual vacancy and collection loss (vs the assessor's stabilized assumption)
- Market capitalization rate support for the property type and submarket
- Recent arm's-length sales of comparable commercial buildings
- Evidence of physical, functional, or economic obsolescence
- Any change in use, tenancy, or condition since the assessment date
How to appeal a commercial assessment in Illinois
- 1Pull the assessment — confirm the assessed value, the assessment ratio/class, and how the assessor derived it (income, cost, or sales).
- 2Build the valuation — capitalize actual net operating income and gather comparable sales to establish market value as of the assessment date.
- 3File before the deadline — submit to County Board of Review (or CCAO in Cook County) by 30 days from publication date (Cook County has specific calendar), with the authorization signed by someone able to bind the owning entity.
- 4Present at the hearing — commercial hearings are evidence-driven; a clean income approach and credible comps carry the day.
Think your Illinois commercial property is over-assessed?
We pull the assessment, build the income-approach case, and file the appeal. Fee: 20% of first-year savings — only if we win. Nothing upfront, and the reduction can hold for years.
Assessment ratios, class rates, and deadlines in Illinois are set by statute and can change year to year, and often vary by county or municipality. Verify current figures and dates with your county assessor or clerk of the board before filing. This page is general information, not legal or tax advice. TaxedFairly is a product of WebLab LLC.