An extension to file is not an extension to pay tax.
Illinois grants both individual and corporate filing extensions automatically, with no application form required to obtain the extension itself. A payment voucher is needed only when tax is owed.
| Item | Detail |
|---|---|
| Form required to get extension | None - automatic |
| Original due date | April 15, 2026 |
| Extended due date | October 15, 2026 (6 months) |
| Extends payment deadline | No - tax is still due April 15, 2026 |
| Longer federal extension | Illinois matches a federal extension that runs longer than 6 months |
| Payment voucher (if owed) | IL-505-I |
| Item | Detail |
|---|---|
| Form required to get extension | None - automatic; IL-505-B only to submit a payment |
| Length | 7 months (8 months for June 30 fiscal-year corporations) |
| Extends payment deadline | No - tax is still due by the original date |
No application form need be filed to obtain either automatic extension. Late-payment penalties and interest accrue from the original due date regardless of a valid filing extension, and a copy of any approved federal extension must be attached to the Illinois return when filed.