Outside Cook, Illinois counties with township government revalue every parcel once every four years. The cycle started in 1995, so 2023 was the last general assessment year and 2027 is the next. That covers Kane, Lake, DuPage, Will, McHenry and Kendall at once.
In a general year every parcel gets a fresh value as of January 1 and every assessment is published. DuPage, for one, mails a notice for every parcel. In Will County, the Board of Review lowered 4,569 assessments in 2019 and 3,212 in 2023, the last two general years. In each other year from 2020 through 2025 it lowered between 1,346 and 2,220.
The filing rule does not change in a general year. A Board complaint is due 30 days after the township's assessments are published. What changes is volume, and in some counties, how late the last townships publish.
Quick Answer
Tax year 2027 is a general reassessment year in all six collar counties. Four of them open Board of Review windows township by township, each closing 30 days after that township's newspaper publication. Will runs one countywide window. Kendall publishes countywide with one final date. No county has posted 2027 dates yet, so firms should staff from the 2026 pattern, expect general-year volume, and watch each county's own publication page. Commercial wins from 2024 through 2026 do not protect the 2027 value.
The rule in plain words
- When. Counties under 3 million people with township government reassess in 1995 and every fourth year after: 2023, then 2027.
- Who publishes. The county's chief assessment office publishes each township's list in a local newspaper. In a general year the list covers every parcel. In other years it covers only parcels that changed, plus a note on any equalization factor.
- The clock. The published notice must state the Board deadline, 30 days after the scheduled publication date. Kane, DuPage, Lake and Kendall all post the same 30-day rule.
- Different cycles. State law lets a county board split a county into four assessment districts on staggered years. None of the six county pages we read shows a township on a different year. DuPage describes 2019 and 2023 as its general years, Kane says township assessors reassess every four years, and Lake's 2026 Board rules say values from 2023 carry forward through 2026.
The county calendar
The 2026 dates below are the latest full pattern. They show the shape of each county's season, not the 2027 dates.
| County | How the window is set | 2026 Board deadlines | Where 2027 dates will post |
|---|---|---|---|
| Kane (16 townships) | 30 calendar days after each township's publication (Board Rule C.10) | July 9 (Dundee) to November 2 (Elgin) | Supervisor of Assessments "Progress Report" page for 2027, which lists notice, publication and deadline dates by township |
| Lake (18 townships) | 30 days after each township's roll is published | August 24 (Benton, Ela) to November 2 (Shields) | Chief County Assessment Office "Assessment Notices" page, with each township's newspaper and dates |
| DuPage (9 townships) | 30 days after legal publication of the township's assessments (Board Rule 8) | September 28 (Wayne) to November 23 (Winfield) | Supervisor of Assessments "Assessment Status" page |
| McHenry (17 townships) | 30 days after each township's publication | August 6 (Richmond) into late November (Marengo, November 30) | Board of Review "Township Filing Deadlines" page and the county's township-by-township news releases |
| Will | One countywide window | August 12 to September 14 (2025: August 6 to September 8) | Supervisor of Assessments complaint process page and the Board's complaint portal |
| Kendall (9 townships) | One countywide publication; final date 30 days later | October 19 | The county's annual assessments site, under its yearly notice to taxpayers |
So what. In 2026 the collar season ran from early July in Kane to late November in DuPage and McHenry. Expect at least that span in 2027, with heavier filing in every township.
What changes in a general year
Later publications are possible. Kane's 2023 deadlines ran from July 14 to December 8, 2023. Its 2026 deadlines ended November 2. A general year can push the last townships into December.
Every parcel gets a notice. DuPage says that in general years a notice goes out for each parcel. In other years only changed parcels get one, and a change from an equalization factor alone gets no mailed notice.
Every value is new. Township assessors set fair cash value as of January 1, working from the prior three years of sales. Kendall's 2026 values rested on 2023 to 2025 sales, so expect 2024 to 2026 sales to drive 2027. In other years most values roll forward with a multiplier. The 2026 factors ran from 1.0590 to 1.0793 in DuPage and up to 1.0741 in Kane.
Records are due at filing. When an income property is appealed on value, Kane and Lake both want three years of income and expense statements with the complaint. Kane gives 14 days after the deadline for evidence. Lake gives 30 days after the deadline for commercial appraisals. DuPage wants evidence at filing and appraisals within 10 days. Kane and Lake both say a corporation needs an attorney.
How a win carries forward, or doesn't
- Owner-occupied homes. A Board or PTAB reduction on an owner's residence stays in effect for the rest of the four-year period, subject to equalization. That period ends with tax year 2026.
- Commercial property. No state rule carries a Board win forward. Assessors may revise any assessment in any year. Lake's Board requires a vacancy-based reduction to be re-proved with a new vacancy affidavit in each later non-general year.
- The PTAB rollover. If PTAB lowers a value after the Board's deadline for a later year in the same four-year period has passed, the owner can appeal those later years straight to PTAB within 30 days of PTAB's decision. That reaches 2024 through 2026 matters, not 2027.
- 2027 resets the base. The general reassessment sets a new value for every parcel. A 2025 reduction is history, not a floor. Every client with a past win needs a fresh read of the 2027 number.
What to do before the first township publishes
- Pull 2024, 2025 and 2026 income and expense statements, rent rolls and leases for every commercial client now.
- List each client's township and its 2026 publication date. Treat that as the earliest likely 2027 date.
- Watch the six county pages weekly from late spring. Kane posted its first 2026 notices in early June.
- Decide which past wins need a new filing. In 2027 they all start over.
- After Board decisions, track the 30-day PTAB clock from each written decision.
Where Censum fits
Censum Docket is built around Cook County, including Board windows by township. Its firm-only commercial desk also includes collar county commercial leads, with comparable state sales and a one-page evidence sheet for each. Censum does not file appeals, is not a law firm and never takes a share of legal fees. The attorney files and makes every legal judgment.
The numbers behind this article
The 2026 and 2023 deadlines come from each county's own pages, read November 11, 2026: Kane's 2023 and 2026 Progress Reports, Lake's Assessment Notices table, DuPage's Assessment Status table and Kendall's assessment site. McHenry's and Will's sites refused or timed out on direct requests. McHenry's 2026 dates come from the county's news releases and Censum's internal windows table; its 30-day pattern was checked against an archived copy of its 2025 deadlines page. Will's windows come from the county's complaint portal and guide as shown in search results. The Will Board counts are Censum's tally of the Will County Board of Review's annual publications of assessment changes, 2017 to 2025, counting rows where the Board's total was below the assessor's. Township counts come from the county tables.
FAQ
Is 2027 a reassessment year for every collar county township?
State law sets 2027 for township-government counties under 3 million people, and none of the six county pages we read shows a township on another cycle. Confirm on each county's page when 2027 notices go out.
Will the 2027 deadlines match 2026?
No. Each deadline runs 30 days from that year's publication, and publications move. Kane's general year ran later than its 2026 season.
Does a 2025 commercial reduction carry into 2027?
No. 2027 is a fresh valuation for every parcel. Only owner-occupied homes get a carry-forward, and that ends with 2026.
When is the PTAB deadline after a collar Board decision?
30 days after the date of the Board's written notice of decision.
Does Censum file collar county appeals?
No. Censum LLC is a data and software company. The firm files and makes every legal judgment.
Sources
- 35 ILCS 200/9-215, general assessment years
- 35 ILCS 200/9-225, four assessment districts
- 35 ILCS 200/9-75, revisions in any year
- 35 ILCS 200/12-10, publication of assessments
- 35 ILCS 200/12-30, mailed notices
- 35 ILCS 200/16-55, Board complaints and the 30-day deadline
- 35 ILCS 200/16-80, homestead carry-forward
- 35 ILCS 200/16-160, PTAB filing
- 35 ILCS 200/16-185, PTAB decisions and later years
- Kane County 2026 Progress Report and 2023 Progress Report
- Kane County Board of Review 2026 Rules and Procedures
- Kane County assessment information
- Lake County Assessment Notices
- 2026 Rules of the Lake County Board of Review
- Lake County Board of Review, important information for 2026
- DuPage County Assessment Status and assessment cycle
- Rules of the DuPage County Board of Review
- McHenry County Township Filing Deadlines
- Will County assessment complaint process and Board of Review complaint portal
- Will County Board of Review 2023 publication (one of the 2017 to 2025 annual publications tallied)
- Kendall County Annual Assessments
- County guides: Kane, Lake, DuPage, Will, McHenry, Kendall
Sources accessed November 11, 2026.
Next step
Put each collar client's township and 2026 publication date on one calendar, and see how Docket's commercial desk handles collar leads. See Censum Docket
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.