When Are S Corp Extensions Due? Form 7004, Dates, and Penalties

S corporation extensions for the 2026 filing season are due March 16, 2026, for calendar-year filers. The rule is the 15th day of the third month after the tax year ends, which is normally March 15, but March 15, 2026, falls on a Sunday, so the IRS treats a filing made the next business day as timely.¹ Filing Form 7004 by that date gives the corporation an automatic six additional months to submit Form 1120-S.

The Deadline Rule

An S corporation files Form 1120-S as an informational return reporting income, deductions, and credits that pass through to shareholders.² The original due date is the 15th day of the third month after the corporation’s tax year ends. For calendar-year filers, that is March 15. When the date falls on a Saturday, Sunday, or federal holiday, the deadline moves to the next business day.¹

To buy more time, the corporation must file Form 7004 by that same original due date. The authority sits in 26 U.S.C. § 6081, which allows the IRS to grant up to six months to file a corporate return when the taxpayer submits the required form and pays any tax owed by the original date.³

Fiscal-year S corporations follow the same structure: the extension request is due the 15th day of the third month after the fiscal year closes.

What the Extension Actually Gets You

A valid extension pushes the Form 1120-S deadline to the 15th day of the ninth month after the tax year ends. For a calendar-year S corporation extending the 2025 return, the new deadline is September 15, 2026, which falls on a Tuesday and needs no weekend adjustment.¹

The extension is automatic. The IRS does not send an approval letter. If Form 7004 was filed on time with correct information, the six months are yours. What the extension does not do is push back the payment date. Any tax the corporation owes at the entity level is still due by the original deadline.⁴

Entity-Level Tax Is Still Due March 16

Most S corporations don’t owe federal income tax because income passes through to shareholders. Two entity-level taxes are the common exceptions, and both are due by the original March 16, 2026, deadline regardless of any extension:²

Built-in gains tax, which can apply when a corporation that used to be a C corporation sells assets that appreciated before the S election.
Excess net passive income tax, which can apply when a former C corporation has accumulated earnings and more than 25% of its gross receipts come from passive sources such as rents, royalties, or interest.

Missing the payment date on either triggers a failure-to-pay penalty of 0.5% of the unpaid amount per month or partial month, up to 25% of the balance, and interest accrues from the original due date.⁵

Filing Form 7004 Correctly

Form 7004 is the Application for Automatic Extension of Time to File Certain Business Income Tax, Information, and Other Returns, available on the IRS website.⁶ The form itself is short, but a few fields decide whether the extension is valid at all.

Enter the corporation’s legal name exactly as it appeared on the most recent return. A mismatch with the IRS database can void the extension.⁷
Provide the corporation’s nine-digit Employer Identification Number.
Include the business address, with suite or unit number, or a P.O. box if mail isn’t delivered to the street address.
Enter the beginning and ending dates of the tax year being extended.
On line 1 of Part I, enter the form code that identifies Form 1120-S. Selecting the wrong return type code is a common rejection cause; check it against the code list in the instructions before submitting.⁷

The IRS recommends filing Form 7004 electronically through its Modernized e-File platform, which returns an immediate confirmation and allows payment through Electronic Funds Withdrawal at the same time.⁸ Certified mail with a return receipt creates a verifiable submission date. The IRS does not acknowledge paper extensions in writing unless there is a problem.

Penalties for Missing the Deadline Without an Extension

If the corporation misses March 16, 2026, and hasn’t filed Form 7004, the late-filing penalty under 26 U.S.C. § 6699 applies per shareholder, per month.⁹ For returns due in 2026, the penalty is $255 per shareholder for each month or partial month the return is late, up to 12 months.¹⁰

The math scales fast with shareholder count. Five shareholders, three months late, is $3,825; the 12-month maximum for that same corporation is $15,300. The penalty also applies when a return is filed on time but incomplete, because failing to include required information such as each shareholder’s Schedule K-1 counts as a failure to file under the statute.⁹

If a penalty notice does arrive, reasonable-cause relief may be available when the corporation can show it exercised ordinary care but still couldn’t file on time. Circumstances such as fires or natural disasters, the death or serious illness of the person responsible for filing, and system issues that blocked a timely electronic submission may qualify; reliance on a tax professional, lack of knowledge, and simple oversight generally do not.¹¹

What the Extension Means for Shareholders

An S corporation’s extension does not extend its shareholders’ individual returns. Shareholders file Form 1040 by April 15 and must request their own extension using Form 4868 if they need more time.¹ These are two separate processes.

The corporation is required to furnish each shareholder a Schedule K-1 by the original filing deadline, March 16, 2026, for calendar-year filers.¹ When the corporation extends because the return isn’t ready, shareholders may not have their K-1s until closer to September, and they generally can’t finish their own 1040 accurately without one. That usually means shareholders need to file their own individual extensions as well. Plan for that timing gap early.

State Extensions Are Separate

A federal extension on Form 7004 does not guarantee extra time for the state return. Some states honor the federal extension automatically, some require a separate state extension form with its own deadline, and a few grant automatic extensions when no state tax is owed. Check with the state tax agency well before the federal deadline, because a missed state extension can generate its own penalties even when the federal extension is valid.

1
Internal Revenue Service. Publication 509 (2026), Tax Calendars
2
Internal Revenue Service. S Corporations
3
Office of the Law Revision Counsel. 26 U.S. Code 6081 – Extension of Time for Filing Returns
4
Internal Revenue Service. Instructions for Form 7004 (12/2025) – Section: Payment of Tax
5
Office of the Law Revision Counsel. 26 USC 6651 – Failure to File Tax Return or to Pay Tax
6
Internal Revenue Service. About Form 7004, Application for Automatic Extension of Time To File Certain Business Income Tax, Information, and Other Returns
7
Internal Revenue Service. Instructions for Form 7004 (Rev. December 2025)
8
Internal Revenue Service. E-filing Form 7004Where to File Form 7004
9
Office of the Law Revision Counsel. 26 U.S. Code 6699 – Failure to File S Corporation Return
10
Internal Revenue Service. Failure to File Penalty
11
Internal Revenue Service. Penalty Relief for Reasonable Cause