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when are s corp taxes due

For most S corporations that use a calendar year, S corp taxes (Form 1120-S) are due on March 15 each year, or the next business day if the 15th falls on a weekend or holiday.

Quick Scoop

  • For the 2025 tax year (filed in 2026), the S corp tax return is due Monday, March 16, 2026 because March 15 is a Sunday.
  • This due date applies to Form 1120-S and to providing Schedule K-1 to each shareholder.
  • You can request a 6‑month extension (to around September 15) by filing Form 7004 by the original March deadline, but this only extends the time to file, not the time to pay any tax owed.

How the deadline works

  • General rule: the S corp return is due on the 15th day of the third month after the end of the S corporation’s tax year.
* Calendar-year S corps (year ends Dec 31): normally due **March 15**.

* If March 15 is on a weekend or holiday, the due date moves to the **next business day** (for 2026, that’s March 16).
  • Fiscal‑year S corps: due on the 15th day of the third month after their fiscal year end (for example, year ending June 30 → due September 15).

Extensions and penalties (story-style mini example)

Imagine your S corp, SunnySide Studio, runs on a calendar year and closes its 2025 books on December 31.

  • You must file Form 1120-S and deliver K‑1s to all shareholders by March 16, 2026.
  • If you know you’ll be running late, you file Form 7004 by March 16 to push the filing deadline to September 15, 2026 —but any tax owed still needs to be paid by March 16 to avoid extra charges.
  • If you don’t file or extend on time, the IRS can charge a monthly penalty per shareholder for every month (or part of a month) the return is late.

In practice, many owners mark mid‑March on the calendar as their “S corp tax day,” with a backup plan to request an extension if the books or K‑1s aren’t ready.

Other dates S corp owners should remember

  • W‑2 to employees/shareholder‑employees : typically due by early February (for 2025 wages, February 2, 2026, in at least one 2026 calendar guide).
  • Quarterly estimated taxes for shareholders (because S corps are pass‑through and tax flows to owners): commonly mid‑April, mid‑June, mid‑September, and the following mid‑January.

TL;DR: For a calendar‑year S corp, your S corp taxes (Form 1120‑S and K‑1s) are generally due March 15 , or the next business day (March 16, 2026, for the 2025 tax year), with a possible extension to September 15 if you file Form 7004 on time.

Information gathered from public forums or data available on the internet and portrayed here.