Partnership Tax Deadlines in Illinois
Federal and state filing dates, extensions, and estimate schedules for 2026.
Illinois filing deadline
Calendar-year due date follows federal timing for pass-through entities.
Due: Mar 16, 2026
Extension: Sep 15, 2026
Form: State partnership return
Estimated payments
No state estimated payment schedule listed.
Due: N/A
FAQ
Does Illinois require Partnership estimated payments?
Estimated payments are not typically required at the entity level, but confirm with Illinois Department of Revenue.
Where can I file Illinois Partnership taxes?
Use Illinois Department of Revenue resources at https://tax.illinois.gov for forms and filing instructions.