Tax Day on April 15 is an important date for individual taxpayers, but it is not the primary federal filing deadline for S corporations. If your business is organized as an S corporation, or an LLC has elected S corporation tax treatment, you generally have an earlier deadline to file your federal business tax return.
Understanding the S corporation tax deadline can help you avoid unnecessary penalties and give shareholders enough time to receive their Schedule K-1 information and prepare their individual tax returns.
When Is the S Corporation Tax Filing Deadline?
An S corporation generally must file Form 1120-S, U.S. Income Tax Return for an S Corporation, by the 15th day of the third month after the end of its tax year. For a calendar-year S corporation, the normal deadline is March 15.
For the 2025 tax year, calendar-year S corporations have a filing deadline of Monday, March 16, 2026, because March 15, 2026, falls on a Sunday.
The same general deadline applies to partnerships filing Form 1065.
Although S corporations are generally pass-through entities, they still have their own federal tax filing obligations. The corporation reports its income, deductions, credits, and other tax information on Form 1120-S. Shareholders generally receive a Schedule K-1 showing their share of the S corporation's tax items, which they use when preparing their individual returns.
S Corporation Tax Deadline for Calendar-Year Businesses
For a calendar-year S corporation filing its 2025 federal return:
Form 1120-S deadline: March 16, 2026
Schedule K-1 deadline: March 16, 2026
Form 7004 extension deadline: March 16, 2026
Extended filing deadline: September 15, 2026
The IRS confirms that Form 7004 generally provides an automatic six-month extension for Form 1120-S.
What If Your S Corporation Uses a Fiscal Year?
Not every S corporation follows the calendar year.
If your corporation uses a fiscal tax year, the federal return is generally due on the 15th day of the third month following the close of the tax year.
For example, if an S corporation's fiscal year ends June 30, its Form 1120-S would generally be due September 15.
If the normal due date falls on a Saturday, Sunday, or legal holiday, the deadline generally moves to the next business day.
Can You Get an Extension for an S Corporation Tax Return?
Yes. An S corporation that needs additional time to complete its return can generally request an automatic extension by filing Form 7004, Application for Automatic Extension of Time to File Certain Business Income Tax, Information, and Other Returns.
For a calendar-year S corporation, Form 7004 is generally due by the original Form 1120-S filing deadline.
For the 2025 tax year, that means the extension request is generally due by March 16, 2026. A timely extension generally moves the filing deadline to September 15, 2026.
An Extension Gives More Time to File, Not More Time to Pay
An extension of time to file should not be confused with an extension of time to pay.
If the S corporation has a federal tax liability that must be paid, the payment generally remains due by the original deadline. Interest may apply to taxes paid late, even when an extension to file has been granted.
While many S corporations generally pass income through to their shareholders, certain S corporations can have federal tax liabilities in specific circumstances. Therefore, businesses should not automatically assume that no payment is required.
What Happens If an S Corporation Files Late?
Failing to file Form 1120-S on time can result in significant IRS penalties.
For S corporation returns due after December 31, 2025, the late-filing penalty is generally $255 for each month or part of a month that the return is late, multiplied by the number of shareholders during any part of the tax year, for up to 12 months. Reasonable-cause relief may be available in appropriate circumstances.
For example, a late return involving several shareholders can result in a substantially larger penalty than a simple flat monthly fee.
The IRS may also impose additional penalties when tax is due and has not been paid.
Because penalties can accumulate quickly, it is important to address a missed deadline as soon as possible rather than waiting for an IRS notice.
Don't Forget the S Corporation Election Deadline
The deadline for filing an S corporation tax return is different from the deadline for electing S corporation status.
Businesses generally use Form 2553, Election by a Small Business Corporation, to make an S corporation election. The election has its own timing requirements and should not be confused with the annual Form 1120-S filing deadline.
Business owners considering an S corporation election should plan ahead to ensure the election is submitted on time.
S Corporation Tax Deadline: Quick Reference
Calendar-Year S Corporation
Form 1120-S due: March 16, 2026
Schedule K-1 due to shareholders: March 16, 2026
Form 7004 extension request: March 16, 2026
Extended Form 1120-S deadline: September 15, 2026
Fiscal-Year S Corporation
Form 1120-S is generally due on the 15th day of the third month after the tax year ends.
Frequently Asked Questions
When is the S corporation tax deadline for 2026?
For calendar-year S corporations filing their 2025 federal tax returns, the deadline is March 16, 2026. The normal March 15 deadline moves to the next business day because March 15 falls on Sunday.
Is the S corporation deadline different from the individual tax deadline?
Yes. S corporations generally file their federal return before the April 15 individual tax deadline. The earlier deadline allows shareholders to receive their Schedule K-1 information before completing their individual tax returns.
Can an S corporation request an extension?
Yes. Eligible S corporations generally use Form 7004 to request an automatic six-month extension to file Form 1120-S.
Does an extension delay payment?
No. An extension generally provides additional time to file, not additional time to pay. Interest can apply when tax is paid after the applicable payment deadline.
What if the S corporation already missed its deadline?
Do not ignore the missed deadline. Filing the required return as soon as possible can help limit additional penalties. If the circumstances qualify, the business may also be able to request penalty relief based on reasonable cause.
Get Help With Your S Corporation Tax Return
S corporation tax filings involve more than simply completing Form 1120-S. The return must properly report the company's income, deductions, shareholder information, and Schedule K-1 amounts.
ContNow Tax Preparation LLC can help small business owners organize their tax information, understand S corporation filing requirements, and prepare for upcoming federal tax deadlines.
Planning ahead is one of the simplest ways to avoid missed deadlines, unnecessary penalties, and last-minute tax filing problems.
Do you have any other questions? Send us an email at 📧 info@contnowtax.com and we’ll get back to you as soon as possible.
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