Cook County reassesses on a three-year cycle, one region at a time, and 2026 is the south and west suburbs' turn. Bremen, Orland and Rich townships, the three Cook townships that serve Tinley Park, are all on the Assessor's 2026 calendar. The values set this year flow into tax year 2026 bills, which are payable in 2027.
That schedule matters because of what the last cycle did. The Cook County Treasurer's analysis of tax year 2023, the previous south-suburban reassessment, found the median residential bill in the south and southwest suburbs rose 19.9%, the largest increase in at least 29 years. The mechanism was not just higher values. The Board of Review cut the assessed value of appealing commercial and industrial properties by more than 21% while trimming appealing residential values only 4.4%, which shifted roughly four percentage points of the region's total tax burden onto homeowners in a single cycle.
+19.9%
Median south-suburban residential bill, tax year 2023 (Cook County Treasurer)
$19.2B
Countywide taxes billed in tax year 2024, the 31st straight annual increase (Treasurer)
+$100.5M
Additional taxes on multifamily of six or more units, tax year 2024 (Treasurer)
Two more changes land at the same time. Starting with the 2026 assessment year, the Assessor values commercial property with a loaded capitalization rate, meaning real estate taxes are no longer deducted as a line-item operating expense in the valuation. And there is no such thing as a single Tinley Park tax rate to model: composite rates across tax codes inside the village ranged from roughly 10.4 to 15.9 per $100 of equalized assessed value in levy year 2020, driven almost entirely by which school districts levy on the parcel.
What we do about it
We underwrite property taxes at full in-place levels and treat every reduction as upside rather than assumption. Tax counsel contests assessments where the evidence supports it and pursues Cook County's Affordable Housing Special Assessment Program where a property qualifies, but neither outcome is ever in our base case. A pro forma that straight-lines taxes through 2027 is not being conservative. It is ignoring a risk that already has a date.
The underwriting question to ask any sponsor in Cook County this year: what tax bill is in the model for 2027, and what happens to the deal if the last cycle repeats?
Sources
- Cook County Assessor, assessment calendar and 2026 capitalization rate policy (updated July 2026)
- Cook County Treasurer, Tax Year 2023 Bill Analysis (June 2024)
- Cook County Treasurer, Tax Year 2024 Bill Analysis (November 2025)
- Village of Tinley Park, property tax rates by tax code (levy year 2020)
Market commentary, not investment advice and not an offer of securities. Figures are as of the sources' stated dates.