Cook County’s property tax system estimates what your home is worth for taxation, hears you out if you disagree, and splits the bill among two million properties. We have measured each step of that machine from the county’s own records. This page is the front door to all of it.
Eight analyses, every figure computed from county files · updated August 14, 2026Is the county’s valuation of your house right?
We matched 11,854 arm’s-length 2025 house sales to their tax-year valuations: the median valuation implied 81 percent of what buyers actually paid, and the gap is widest on the South Side — the ground the 2027 reassessment will remeasure. Assessments versus sale prices, by neighborhood.
Should you appeal — and do you need a lawyer?
In 2025, Chicago homeowners who appealed at the Board of Review without a lawyer won a reduction 59.5 percent of the time; appeals filed by lawyers won 38.9 percent. Filing is free at both county offices. The lawyer-versus-alone numbers.
What happens after a first no?
The Assessor’s office turned down five appeals in six at stage one — and 93 percent of those parcels also appeared at the Board of Review, where 42.5 percent received the reduction stage one had refused. The two-stage appeal, followed parcel by parcel.
Who actually files?
Citywide, 17.5 of every 100 houses appealed for tax year 2025 — but nearly half of Lincoln Park’s houses did, against about one in 24 on the Southeast Side, and the low-filing areas won more often when they did file. The appeal map.
Where does the appeal relief go?
Appeals removed $3.85 billion of assessed value from Chicago’s 2025 roll. Measured against its own value, commercial property was cut 17.0 percent and residential 1.3 percent — thirteen to one. Within a shared taxing district, value removed from one class shifts relative burden toward the rest, though individual bills also turn on levies, exemptions and equalization. Where the reductions went.
Why are the bills late?
Cook County was late on three of its last four second-installment deadlines — due dates of December 30, 2022, December 1, 2023, and December 15, 2025, with only 2024’s bill on schedule — and says this year’s bill will run about two months behind as well, with no due date set as of August 14, 2026. The county names its system modernization as the cause; CPS has said it is short $250 million while it waits, and the Treasurer’s office says at most $80 million. The full ledger of due dates · the late-collections dispute.
The other carrying cost
Property taxes are not the only carrying cost that moves on you. Illinois home insurance premiums rose 32 percent in four years, and the new state law does not touch bills until July 2027. The insurance arc.
How this hub works
Analyses join this page as they publish, and the figures above refresh whenever a piece is updated; tax-year-2026 numbers get a full revisit when the county certifies them. Every piece discloses its sources, its screens, and what it deliberately does not claim — including where we suppress thin data rather than guess. Nothing here is tax or legal advice; filing windows and forms live at the county’s own offices, linked from each analysis. If you spot an error anywhere in the cluster, corrections come first.