The federal filing deadline for calendar year 2025 partnership (Form 1065) and S Corporation (Form 1120S) tax returns is Monday, March 16, 2026. Tax professionals and business owners should ensure returns are filed or properly extended by this date to avoid penalties.
E-File Rejection Grace Period
If a federal partnership or S Corporation return is e-filed on March 16 but rejected, the return will still be considered timely filed as long as it is corrected, retransmitted, and accepted by March 26, 2026.
Disaster Relief Filing Extensions
The IRS has granted filing and payment extensions for businesses and individuals affected by certain natural disasters. Eligible taxpayers in the following areas have additional time to file various federal tax returns and make payments.
March 30, 2026 — Missouri
Businesses and individuals in parts of Missouri affected by severe storms, straight-line winds, tornadoes, and flooding beginning March 30, 2025 now have until March 30, 2026 to file applicable federal individual and business tax returns and make tax payments.
For more information, see IRS News Release MO-2025-03, which outlines relief for taxpayers impacted by severe weather events in multiple Missouri counties.
March 31, 2026 — Louisiana
Businesses in the State of Louisiana affected by severe winter ice storms beginning January 22, 2026 now have until March 31, 2026 to file certain federal tax returns and make payments.
Additional details are available in IRS News Release LA-2026-01, which explains the tax relief provided for impacted Louisiana taxpayers.
May 1, 2026 — Montana and Washington
Montana
Businesses and individuals affected by severe storms and flooding beginning December 10, 2025 have until May 1, 2026 to file applicable federal returns and make tax payments.
See IRS News Release MT-2026-02 for full details on relief provided to Montana taxpayers.
Washington
Businesses and individuals in Washington State impacted by severe storms, straight-line winds, flooding, landslides, and mudslides beginning December 9, 2025 also have until May 1, 2026 to file applicable federal tax returns and make payments.
More information is available in IRS News Release WA-2025-03.
Filing an Extension for Partnership or S Corporation Returns
If additional time is needed to complete a 2025 partnership or S Corporation return, taxpayers can request an automatic extension until September 15, 2026 by filing Form 7004, Application for Automatic Extension of Time to File Certain Business Income Tax, Information, and Other Returns.
It is important to remember that an extension provides additional time to file the return, not additional time to pay taxes owed. If a partnership or S Corporation expects to owe tax, payment should be submitted when filing the extension to avoid potential penalties and interest.
