Business Tax Extensions

S Corporation Tax Extension: Form 7004 for Form 1120-S

S corporations get one of the earliest business deadlines of the year — and one of the most expensive penalties for missing it, charged per shareholder even when no tax is owed. One Form 7004 moves the deadline six months, automatically.

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Quick Answer

An S corporation extends Form 1120-S by filing Form 7004 with form code 25 by the return’s regular due date — March 16, 2026 for calendar-year 2025 returns (March 15 is a Sunday). The extension is automatic and adds 6 months, to September 15, 2026. It extends the filing and the K-1s, not the payment of any entity-level tax.

Why the S corp deadline catches people

Form 1120-S is due the 15th day of the 3rd month after year end — a full month before the individual and C corporation deadline most owners have in their heads. The early date exists so shareholders can receive their Schedule K-1s in time to file their own returns by April. Miss it without an extension and the penalty clock starts immediately: an indexed dollar amount per shareholder, per month, up to 12 months — payable even when the corporation owes no tax at all. For a four-shareholder company that forgets until summer, that is four multiplied by every late month.

Filing the extension, step by step

  1. Enter form code 25 (Form 1120-S) on line 1 of Form 7004, with the corporation’s exact legal name and EIN as registered with the IRS — a name-control mismatch is the most common e-file rejection.
  2. Confirm the tax year on line 5a (calendar 2025, or the fiscal dates).
  3. Estimate any entity-level tax on lines 6–8. For most S corps this is zero; former C corporations subject to built-in gains tax or excess net passive income tax must estimate and pay those by the original deadline.
  4. Transmit by March 16, 2026 and keep the electronic acknowledgment — it is your proof the extension went in on time.

What the extension does for shareholders

K-1s travel with the return, so extending the 1120-S effectively extends the K-1s to September 15. Shareholders who cannot file their personal returns without those numbers typically file Form 4868 for their own 6-month extension — but their personal tax payment is still due April 15. The clean pattern for an extended S corp: shareholders estimate their pass-through income, pay with their 4868, and reconcile when the K-1 arrives.

Six more months, one short form

E-file Form 7004 in minutes and keep the IRS acknowledgment as proof of timely filing.

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S corp extension FAQs

When is the S corp extension deadline in 2026?
Form 7004 must be filed by the regular Form 1120-S due date: the 15th day of the 3rd month after the tax year ends. For calendar-year 2025 returns that is March 16, 2026, because March 15 falls on a Sunday. The extension then runs six months, to September 15, 2026.
Which form code does an S corporation use on Form 7004?
Code 25 — the Form 1120-S entry on line 1 of Form 7004 (Rev. December 2025). Entering the wrong code can invalidate the extension for the return you meant to extend, so it is worth double-checking.
Does the extension also delay Schedule K-1s to shareholders?
Effectively yes. Schedule K-1s are prepared and furnished with the Form 1120-S, so a valid extension moves both to the extended deadline. Shareholders who file their personal returns before receiving a K-1 usually extend their own Form 1040 with Form 4868.
Do S corps owe tax with the extension?
Usually not at the entity level — an S corporation is a pass-through, and income is taxed to shareholders. But there are exceptions (built-in gains tax and excess net passive income tax for some corporations that were formerly C corps), and any entity-level tax due must still be estimated and paid by the original deadline. The extension never extends time to pay.
What is the penalty for filing Form 1120-S late?
A per-shareholder, per-month penalty — a dollar amount the IRS indexes annually, charged for each shareholder for each month (or part of a month) the return is late, for up to 12 months. It applies even when no tax is due, which is why the extension matters for S corps despite pass-through status. A separate penalty applies for failing to furnish K-1s.

Related guides: Form 7004 overview, every Form 7004 code, late-filing penalties explained.

Disclaimer: Deadlines shift with weekends and holidays and penalty amounts are indexed annually; verify current figures in the IRS Form 7004 and Form 1120-S instructions. This page is general information, not tax advice. TaxFilingCenter is an IRS-authorized e-file provider and does not provide legal or tax advice.