In 2024, the year the Assessor reassessed the City of Chicago, the Cook County Board of Review issued 324,618 PIN-level decisions on Chicago residential property. In 2023 it issued 119,135. In 2025, 162,157. The Cook County Clerk's 2025 tax rate report says Chicago will be reassessed again for tax year 2027.
That spike is the loudest moment in the county's tax year. It is not the only one. Every step from January to December gives you a specific, useful reason to contact a past client, and none of them requires tax advice.
Quick Answer
Chicago's 2024 reassessment year produced 324,618 residential Board decisions, 2.7 times the 2023 count, and Chicago is reassessed next for tax year 2027. Around that peak, the year runs on a steady rhythm: January 1 sets exemption eligibility, the first-installment bill comes due in spring, exemption filing opens in spring, Assessor windows run township by township from spring into December, Board windows follow, and the second-installment bill shows the exemption lines. Each step is a reason to call.
The reassessment year, by the numbers
Cook County reassesses one region a year. Residential PIN-level decisions at the Board of Review in the last cycle, with each region's reassessment year marked:
- South and west suburbs: 110,214 in 2023 (reassessed), 77,780 in 2024, 67,391 in 2025.
- City of Chicago: 119,135 in 2023, 324,618 in 2024 (reassessed), 162,157 in 2025.
- North suburbs: 101,495 in 2023, 87,833 in 2024, 218,236 in 2025 (reassessed).
In every region, the reassessment year was the biggest of the three.
The rotation ahead:
- 2026: south and west suburbs (under way now)
- 2027: City of Chicago
- 2028: north suburbs
If your past clients are in Chicago, 2027 is the year their values are reset. Plan the year's contact around it.
Early in the year: January 1 and the first installment
January 1 decides exemptions. Eligibility for the homeowner exemption depends on who owned and occupied the home on January 1 of the tax year. The senior exemption can be prorated for a senior who moves in later in the year. Clients who moved in during the prior year are now eligible for the year that just began, though they will not file for it until the following spring.
The first-installment bill. It is an estimate, 55% of the prior year's total, and it carries no new exemptions or values. The due date moves: the tax year 2023 first installment was due March 1, 2024, tax year 2024's on March 4, 2025, and tax year 2025's on April 1, 2026.
Reason to call: "Your first-installment bill is an estimate based on last year. It won't show your exemptions yet. That comes on the second bill."
Spring: exemption filing season
The Assessor opens online filing for the prior tax year's exemptions in spring. For tax year 2025, filing opened March 9, 2026.
Reason to call buyers from the year before last: "If you were living in the home on January 1 last year, you can apply for that year's homeowner exemption now. It's free to apply, and it renews automatically after that."
The timing surprises people. A buyer who closed in mid-2025 was not there on January 1, 2025, so their first eligible year is tax year 2026, filed in spring 2027.
The homeowner and senior exemptions renew automatically. The Senior Freeze does not: it must be filed every year, and the income limit is rising, from $65,000 for tax year 2025 to $75,000 for 2026.
Spring into December: Assessor windows
Each township gets its own Assessor appeal window, whether or not its region is being reassessed that year. Outside the reassessment region, only owners whose value changed get a notice. In the Assessor's 2026 calendar:
- The first notices went to Norwood Park on April 13.
- Each township's last file date fell about six weeks after its notice date.
- The last window, Bloom's, closes December 17, 2026.
Reason to call: "Your township's notice just mailed. It's a value, not a bill. The appeal deadline is printed on it, and there are no extensions."
Late summer into winter: Board of Review windows
The Board of Review opens its own township windows, in groups, after the Assessor finishes each township. The Board's 2026 schedule, as posted on November 12, 2026:
- Group 1: Evanston, New Trier, Norwood Park, Oak Park, River Forest, Riverside, Rogers Park. Open August 3, closed September 1, evidence due September 11.
- Group 2: Berwyn, Cicero, Elk Grove, Lakeview, Maine, Palos. Open August 31, closed September 29, evidence due October 9.
- Group 3: Lyons, Northfield, Stickney, West Chicago. Open October 8, closed November 6, evidence due November 16.
- Group 4: Barrington, Bremen, Calumet, Hyde Park, Lemont. Open November 9, closes December 8, evidence due December 18.
That is 22 of 38 townships. The Board posts the rest after the Assessor finishes each township, so check its dates page monthly.
Reason to call: "If you appealed at the Assessor and got no change, the Board of Review is a separate second chance, and your township's window is open."
Fall: the second-installment bill
This is the bill that applies the new values and the exemptions. Its due date moves more than any other: August 1, 2024 for tax year 2023, December 15, 2025 for tax year 2024, and October 1, 2026 for tax year 2025.
Reason to call: "Your second-installment bill is the one that shows exemption lines. If one you expected is missing, it can usually be fixed."
Anytime
Missing exemptions from past years. The Assessor's Certificate of Error process currently covers tax years 2021 through 2025. The Treasurer issues any refund.
After a Board decision. An owner who wants to go further can appeal to the Property Tax Appeal Board within 30 days of the postmark date on the Board's written decision.
How to use the calendar without being salesy
- One useful fact per message. Lead with the date or deadline.
- Segment on property and township facts only. Never on a client's age, family status, or anything that stands in for a protected characteristic. If a message mentions senior relief, send it to everyone and let people self-select.
- Point to official sources. Link the Assessor's or Board's page.
- Do not judge the value. Say a notice "may be worth checking", not that a client is over-assessed.
Where Censum House fits
Censum House includes a Township Tax Calendar with Assessor and Board windows across all 38 townships, a Weekly Reasons-to-Call Digest sent every Monday under your brand, and a Past Client Monitor that watches your book for exemption gaps and open windows.
The numbers behind this article
Decision counts are Censum's tabulation of the Cook County Board of Review Appeal Decision History dataset (county open data, 7pny-nedm), last updated by the county on June 9, 2026. They are PIN-level residential decisions, not complaints, and include condominium units. Regions follow the Assessor's triads: Chicago's eight townships, 13 north suburban townships and 17 south and west suburban townships. Censum is independent and is not affiliated with Cook County or any government agency.
FAQ
Are the dates the same every year?
No. Bill due dates, filing seasons and township windows all move. The second installment alone has fallen in August, December and October in the last three years.
Which townships are reassessed next year?
The eight City of Chicago townships, for tax year 2027. The Cook County Clerk's 2025 tax rate report states it.
How much busier is a reassessment year?
In Chicago's 2024 reassessment year the Board issued 324,618 residential decisions there, against 119,135 the year before. The north suburbs went from 87,833 in 2024 to 218,236 in their 2025 reassessment year.
Can I tell a client they should appeal?
Share the signal and the deadline. The decision, and any advice about value, belongs to the owner and their advisor.
Sources
- Cook County Assessor, Assessment Calendar and Deadlines
- Cook County Assessor, Property Tax Exemptions
- Cook County Assessor, Certificates of Error
- Cook County Treasurer, Important Dates
- Cook County Board of Review, Dates and Deadlines and its 2026 session schedule
- Cook County Clerk, Tax Extension and Rates: 2025 Tax Rate Report, released September 23, 2026
- Illinois Property Tax Appeal Board, FAQ
- Censum tabulation of the Cook County Board of Review Appeal Decision History dataset (Cook County open data), accessed November 7, 2026; PIN-level decisions; dataset last updated June 9, 2026.
Next step
See every Assessor and Board window for your farm in one place. See the Township Tax Calendar in Censum House
Censum LLC is a data and analytics company, not a law firm and not a tax advisor. Censum is independent and is not affiliated with Cook County or any government agency.