Cook County property assessments

What the county's own roll says, and how many parcels sit above their neighbours.

1,878,782parcels on record

1,766,481with a published assessment

$27,000median assessed value

373,954above their neighbourhood median

Among those, the typical excess is $13,221 of assessed value above the median for like-classified land in the same town — $4,944,077,129 in total across Cook County.

roughly 1 in 5 Cook County properties is assessed above its local median. Whether yours is one of them takes a few seconds to find out — the comparison runs against the same 1,766,481 assessed parcels shown above.

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Free to check. Nothing is filed on your behalf, and a verdict of "not worth appealing" is the answer we return most often.

A median has half of everything above it by definition, boards do not grant every uniformity claim, and being above a median is a ground to argue rather than proof of error. These are assessed values, not tax bills.

Your deadline in Cook County

30 days from the publication of your TOWNSHIP's assessment roll. Cook reassesses on a rolling three-year, township-by-township calendar, so your window depends on your township and not on the county.

Statutory basis: 35 ILCS 200/16-55. A late filing cannot be cured, so confirm the date on your own notice — it is not the same across the county.

How the assessment was calculated

Illinois assesses at 10% of market value, except in Cook County, which uses its own classification ordinance with residential property at 10%. The assessor estimates market value by mass appraisal — a model over recent sales, adjusted by the characteristics they hold on file for your property. If those characteristics are wrong, the number is wrong. The full anatomy is here.

The argument most people miss

Beyond “my house is worth less than they say”, the Illinois Constitution requires uniform taxation. If comparable property near you is assessed at a lower rate per square foot, that is a ground for relief in its own right — no appraisal needed, and built from figures the assessor published themselves.

Towns in Cook County

Chicago — 884,264 parcels Orland Park — 39,587 parcels Des Plaines — 31,383 parcels Arlington Heights — 30,759 parcels Schaumburg — 28,978 parcels Palatine — 27,793 parcels Evanston — 26,575 parcels Oak Lawn — 25,867 parcels Skokie — 25,073 parcels Tinley Park — 21,404 parcels Glenview — 21,005 parcels Mount Prospect — 19,245 parcels Oak Park — 18,755 parcels Hoffman Estates — 18,284 parcels Northbrook — 18,166 parcels Cicero — 17,334 parcels Park Ridge — 16,490 parcels Berwyn — 15,604 parcels Calumet City — 15,400 parcels Chicago Heights — 14,881 parcels Harvey — 14,490 parcels Streamwood — 14,426 parcels Elk Grove Village — 13,976 parcels Wheeling — 13,515 parcels Lansing — 12,858 parcels Niles — 11,836 parcels Wilmette — 10,929 parcels Morton Grove — 10,721 parcels Oak Forest — 10,686 parcels Lemont — 10,461 parcels Burbank — 9,992 parcels South Holland — 9,498 parcels Melrose Park — 9,469 parcels Dolton — 9,386 parcels Rolling Meadows — 9,254 parcels Markham — 9,018 parcels Evergreen Park — 8,948 parcels Homewood — 8,914 parcels Brookfield — 8,811 parcels Elgin — 8,562 parcels

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Three things you can run right now, free

See a real analysis first

A genuine run against a real Illinois property, generated when you open the page — the verdict, the comparable parcels, and every step of the arithmetic. Nothing to type.

Sales Reality Check

A full IAAO sales-ratio study for any Cook PIN: the level your neighbourhood is really assessed at, how evenly it is applied, and every arm's-length sale it used.

The Twin Test

The parcels the county's own records describe the same way as yours — same class, same town, same size — and what each of them is assessed.

Portfolio Triage

More than one property in Cook County? Paste up to 1,000 PINs and get the whole book ranked by what an appeal is actually worth — including which ones to drop.