All 102 Illinois counties and county equivalents. 5 have been checked against the county's own schedule; the rest follow the state schedule below.
| Instalment | Due | Notes |
|---|---|---|
| 1st installment | June 2, 2027 | Statutory backstop; the date printed on the county's bill controls if it is later than June 1. |
| 2nd installment | September 2, 2027 | Statutory backstop for the second installment, again subject to the printed bill date. |
Illinois property tax is billed and collected county by county, so the collector — not the state — issues the bill. Every county collector prints its own dates, and Cook County's spring and late-summer schedule differs from the June and September pattern in most other counties.
CountyTaxDates is an independent reference and is not a government agency. Deadlines change and exceptions apply — always confirm with your county treasurer using the official link on this page. Nothing here is tax, legal or financial advice.