Cook County, IL — Property Tax Underwriting Guide
Illinois · Sale-event triggered
What this means for multifamily underwriting
Cook is a three-step calc: market value × 25% (commercial LOA) × state equalizer = EAV, then × local rate. Confirm whether the subject sits in the current reassessment township.
Transaction type breakdown
Reassessment is on a 3-year township cycle rather than directly sale-triggered, but a recent arm's-length sale is strong evidence of value and often pulls the next assessment toward the price.
Refinance does not trigger reassessment.
Ownership change is not itself a trigger; the township cycle and equalization drive value.
Tax appeal information
Appeal timing is township-specific; official guidance directs users to the Assessor's per-township calendar rather than one countywide date. LOA, equalizer, and rate should each be validated for the parcel.
Guide review
County guidance last reviewed: July 16, 2026
Tax-rate scope: County-level underwriting placeholder; not a parcel-specific tax rate.
Official sources: Assessor, Assessment calendar & deadlines, Treasurer
Class 3 apartments are assessed at 10% of market value. Chicago's 2023 general composite rate is 6.995% (69.95 mills) per the Cook County Clerk Tax Rate Report; the 2024 final equalizer is 3.0355 per the Illinois Department of Revenue. Chicago-representative county-level rate; confirm the parcel's tax code because composite rates vary by township and community area.
Sources
Parclio estimates are underwriting guidance, not legal or tax advice. Always verify millage rates, the seller's assessed value, and appeal deadlines with the county assessor or local counsel before relying on these numbers for a credit decision.
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