Here’s what HIVE AI had to say about “What are the key IRS deadlines for filing and payments during the 2026 filing season, including extensions and estimates?”:
2026 filing season (tax year 2025 returns): core individual deadlines
- IRS starts accepting 2025 individual returns on January 26, 2026. 1
- Individual Form 1040 filing deadline: April 15, 2026. 1 2
- Payment deadline (even if you extend): any tax due for 2025 is still due April 15, 2026; an extension to file is not an extension to pay. 2 3
Extensions (individuals)
- File Form 4868 (or get an automatic extension via an extension-designated e-payment) by April 15, 2026. 2 4
- If you timely extend, the extended filing deadline is October 15, 2026 (pushed to the next business day if Oct. 15 is a weekend/holiday). 5
- Special automatic 2-month filing extension for certain taxpayers outside the U.S./Puerto Rico (Form 4868 box 8 or 9): Form 4868 is treated as timely if received by June 15, 2026 (but interest generally still applies if tax isn’t paid by April 15). 4
Estimated tax deadlines during calendar year 2026 (for tax year 2026)
For individuals, 2026 estimated tax installment due dates are: April 15, 2026; June 15, 2026; September 15, 2026; and January 15, 2027 (next business day if a weekend/holiday). 6
Key business return deadlines commonly encountered in the 2026 season (calendar-year filers)
- S corporations (Form 1120-S): due March 15, 2026; extended due September 15, 2026 if a timely extension is filed. 7
- C corporations (Form 1120, calendar year): due April 15, 2026; extended due October 15, 2026 if a timely extension is filed. 7
Sources
1 – IRS Newsroom – IR-2026-02 📄 Summarize
2 – When to file
3 – IRS: Need more time to file, request an extension
4 – 3.11.212 Applications for Extension of Time to File
5 – Due dates & extension dates for e-file
6 – Estimated tax | Internal Revenue Service
7 – Internal Revenue Bulletin: 2025-38
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