Illinois business filing due dates
The Illinois deadlines Ordexly tracks for Oct 2026 to Oct 2027. Every date links to the agency page it was checked against (last checked ). Which ones apply to a business depends on its registrations and filing frequency, so confirm with the agency.
Annual report based on formation date
Illinois Annual Report (before anniversary month). Illinois annual report (corporations 805 ILCS 5/14.10; LLCs 805 ILCS 180/50-1(b)) must be delivered within the 60 days before the first day of the anniversary month, so Ordexly shows the last weekday of the month before the anniversary month. Corporations with an extended filing month use that month instead. Official source.
Ordexly works out this date for each business from its formation month.
Sales & use tax
| Due | Deadline | Source |
|---|---|---|
| Illinois ST-1 Sales and Use Tax (monthly) October 2026 | official source | |
| Illinois ST-1 Sales and Use Tax (monthly) November 2026 Moved from Sun, Dec 20 (weekend). | official source | |
| Illinois ST-1 Sales and Use Tax (monthly) December 2026 | official source | |
| Illinois ST-1 Sales and Use Tax (quarterly) Q4 2026 | official source | |
| Illinois ST-1 Sales and Use Tax (monthly) January 2027 Moved from Sat, Feb 20 (weekend). | official source | |
| Illinois ST-1 Sales and Use Tax (monthly) February 2027 Moved from Sat, Mar 20 (weekend). | official source | |
| Illinois ST-1 Sales and Use Tax (monthly) March 2027 | official source | |
| Illinois ST-1 Sales and Use Tax (quarterly) Q1 2027 | official source | |
| Illinois ST-1 Sales and Use Tax (monthly) April 2027 | official source | |
| Illinois ST-1 Sales and Use Tax (monthly) May 2027 Moved from Sun, Jun 20 (weekend). | official source | |
| Illinois ST-1 Sales and Use Tax (monthly) June 2027 | official source | |
| Illinois ST-1 Sales and Use Tax (quarterly) Q2 2027 | official source | |
| Illinois ST-1 Sales and Use Tax (monthly) July 2027 | official source | |
| Illinois ST-1 Sales and Use Tax (monthly) August 2027 | official source | |
| Illinois ST-1 Sales and Use Tax (monthly) September 2027 | official source | |
| Illinois ST-1 Sales and Use Tax (quarterly) Q3 2027 | official source |
Payroll & withholding
| Due | Deadline | Source |
|---|---|---|
| Illinois IL-941 Withholding Return Q3 2026 | official source | |
| Illinois IL-941 Withholding Return Q4 2026 | official source | |
| Illinois IL-941 Withholding Return Q1 2027 | official source | |
| Illinois IL-941 Withholding Return Q2 2027 | official source |
Unemployment / reemployment
| Due | Deadline | Source |
|---|---|---|
| Illinois IDES UI-3/40 Q3 2026 | official source | |
| Illinois IDES UI-3/40 Q4 2026 | official source | |
| Illinois IDES UI-3/40 Q1 2027 | official source | |
| Illinois IDES UI-3/40 Q2 2027 | official source |
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Nearby: Indiana due dates · Iowa due dates · Kentucky due dates · Missouri due dates · Wisconsin due dates
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