Blog · Illinois · 2026-08-01 · 2 min read

The Illinois property tax calendar, and why you pay a year late

Assessed one year, billed the next. Everything about timing follows from that.

Illinois property taxes are paid in arrears, which explains most of the confusion about timing.

The sequence

1. 1 January — the assessment date. Ownership, occupancy and condition are judged as of this day.
2. Spring to autumn — assessors work, then publish assessment lists by township.
3. 30 days from publication — the Board of Review appeal window for that township.
4. Autumn to winter — the Department of Revenue issues the county equalization factor.
5. Late in the year — taxing bodies adopt levies; the clerk computes rates.
6. The following year — bills issue, generally in two instalments.

The consequence

An appeal filed this summer affects the bill you receive next year. There is no mechanism to reduce the bill already in your hand — that one reflects last year's assessment, whose window has closed.

What to do with this

Act on the notice, not on the bill. By the time a bill makes you angry, the assessment behind it is final. The notice is the moment the system is still open to you.