Tax deadlines for 2026 and 2027
The federal and Illinois dates a calendar-year small business and its owners meet, with weekend and holiday shifts already applied. Each one links to the article that explains it.
2026
| Due | What is due |
|---|---|
| Thursday | Fourth 2025 estimated tax payment Last federal (Form 1040-ES) and Illinois (IL-1040-ES) estimated payment for 2025. |
| Monday | W-2s and 1099-NECs for 2025 Forms W-2 to employees and the Social Security Administration, Forms 1099-NEC to contractors and the IRS, and W-2s to the Illinois Department of Revenue. January 31, 2026 was a Saturday. |
| Monday | 2025 partnership and S corporation returns Form 1065 or Form 1120-S for 2025 with the owners’ Schedule K-1s, or Form 7004 for six more months. IL-1120-ST for 2025 is due too. March 15, 2026 was a Sunday. |
| Wednesday | 2025 individual and C corporation returns, first 2026 estimated payment Form 1040 and IL-1040 for 2025 (or Form 4868 to extend), Form 1120 (or Form 7004), IL-1065 for Illinois partnerships, and the first 2026 estimated payment, federal and Illinois. |
| Monday | Second 2026 estimated tax payment Federal and Illinois payment for income earned April 1 to May 31, 2026. |
| Tuesday | Third 2026 estimated payment, extended 2025 partnership and S corporation returns Federal and Illinois payment for income earned June 1 to August 31, 2026, and 2025 Forms 1065 and 1120-S on extension. |
| Thursday | Extended 2025 individual and C corporation returns 2025 Forms 1040, IL-1040 and 1120 on extension. Illinois gives partnerships (IL-1065) and S corporations (IL-1120-ST) until this date without asking. |
2027
| Due | What is due |
|---|---|
| Friday | Fourth 2026 estimated tax payment Last federal and Illinois estimated payment for 2026, for income earned September 1 to December 31. |
| Monday | W-2s and 1099-NECs for 2026 Forms W-2 to employees and the Social Security Administration, Forms 1099-NEC to contractors paid $2,000 or more and to the IRS, and W-2s to the Illinois Department of Revenue. January 31, 2027 is a Sunday. |
| Monday | 2026 partnership and S corporation returns Form 1065 or Form 1120-S for 2026 with the owners’ Schedule K-1s, or Form 7004 to extend. IL-1120-ST for 2026 is due the same Monday. |
| Thursday | 2026 individual and C corporation returns, first 2027 estimated payment Form 1040 and IL-1040 for 2026 (or Form 4868), Form 1120 (or Form 7004), IL-1065 for Illinois partnerships, and the first 2027 estimated payment, federal and Illinois. |
| Tuesday | Second 2027 estimated tax payment Federal and Illinois payment for income earned April 1 to May 31, 2027. |
| Wednesday | Third 2027 estimated payment, extended 2026 partnership and S corporation returns Federal and Illinois payment for income earned June 1 to August 31, 2027, and 2026 Forms 1065 and 1120-S on extension. |
| Friday | Extended 2026 individual and C corporation returns 2026 Forms 1040, IL-1040 and 1120 on extension, and the automatic Illinois extension date for 2026 IL-1065 and IL-1120-ST returns. |
2028
| Due | What is due |
|---|---|
| Tuesday | Fourth 2027 estimated tax payment Last federal and Illinois estimated payment for 2027. January 15, 2028 is a Saturday and January 17 is Martin Luther King Jr. Day. |
How to read these dates
These are the dates for a business whose tax year ends December 31. A business on a fiscal year moves each date by the same number of months.
An extension gives more time to file, not to pay. Tax owed is still due on the original date, federal and Illinois.
The IRS postpones deadlines for counties hit by a declared disaster. If that may apply to you, check IRS.gov/disasters before relying on a date here.
Dates checked on October 5, 2026 against IRS Publication 509 (2026), the 2026 Form 1040-ES and Illinois Department of Revenue instructions. The 2027 dates follow the same rules and are checked again when the IRS publishes its 2027 calendar. Articles on this site are general information for small-business owners. They are not tax, legal or accounting advice for your situation, and reading them does not make you a client.
Have us keep track of these dates
Planning and payroll clients hear from us before each date that applies to them, with the amount to send if there is one. Book a free 30-minute consult to see which dates apply to your business.
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