Key Takeaways

  • The S corp tax filing deadline is typically March 15 (or the 15th day of the third month after the end of the tax year).
  • Form 1120S must be filed by this date, reporting the corporation’s income, deductions, and credits.
  • Extensions are available by filing Form 7004, giving S corps up to six additional months—usually until September 15.
  • Shareholders must also file their individual returns by April 15, reporting their share of the corporation’s income via Schedule K-1.
  • Missing the S corp filing deadline can trigger penalties of $210 per shareholder per month, up to 12 months.
  • Businesses operating on fiscal years have due dates that fall on the 15th day of the third month after the fiscal year ends.
  • Quarterly filing dates, estimated payment deadlines, and specific extensions for holidays and weekends affect compliance.

The S corporation tax return due date falls on the same date each year, March 15. It includes the possibility of a six-month extension if you file Form 7004. S corporations have to file an annual tax return, among a number of other documents, to the IRS. These taxes mainly relate to the wages that are paid to the company's employees.

S-Corp Federal Tax Filing Dates 

"Pass-through" entity means the income and losses of the corporation go directly to the shareholders. In turn, they report it on their individual tax returns. The shareholders also pay the taxes on the profits and the losses. 

An S corporation is required to submit a number of forms related to the taxes withheld from employee wages to the IRS, including an annual informational income tax return. It is required for all S corporations to file their annual tax returns. This day typically lands on March 15, or the 15th of the third month of the year following the tax year's end. A corporation must record its financial activity and include this information on Form 1120S, as well as attach a Schedule K-1 per shareholder. 

It is possible for a corporation to file for an extension, which adds six months to the March 15 filing date, by submitting IRS Form 7004. Shareholders are subject to the same income taxes demanded of all individual taxpayers. This means that shareholders who are paying tax on corporate income are subject to the annual April 15 deadline. 

An S corporation will have to withhold federal income tax, Medicare taxes, and Social Security from paychecks if it pays dividends to its employees. To do this, an S corporation will need to file IRS Form 941, and it must report the estimated amount that the company will withhold and transfer to the IRS every quarter on:

  • October 31
  • January 31
  • April 30
  • July 31

Understanding Fiscal Year vs. Calendar Year S Corp Deadlines

Most S corporations follow a calendar tax year, meaning their tax year ends on December 31 and their S corp tax filing deadline is March 15. However, some corporations use a fiscal year ending on a different date. In those cases, the return is due by the 15th day of the third month after the fiscal year ends. For example, if a corporation’s fiscal year ends June 30, the tax filing deadline would be September 15.

S corporations must also ensure that estimated quarterly taxes and other required payroll tax forms (Forms 941 and 940) are submitted throughout the year. Failure to align filing and payment schedules with the company’s fiscal calendar can lead to missed deadlines and penalties.

S Corporation 1120S Return Due Date

The filing deadline for Form 1120S is the 15th day of the third month following the tax year's end. This date is March 15, 2017 for corporations on the calendar year. The tax filing date for corporations that are due to dissolve is also the 15th day of the third month following the end of the year. If the tax due date lands on a legally recognized holiday or Saturday or Sunday, the business can file the following day that is not one of the aforementioned days. 

An S corporation must submit Form 1120S by the appropriate due date if the S corporation election ends and returns to a C corporation. This includes extension dates. To request an extension lasting six months, file Form 7004 Application for Automatic Extension of Time to File Certain Business Income Tax, Information, and Other Returns by the usual return due date.

Penalties for Missing the S Corp Tax Filing Deadline

If an S corporation fails to file its Form 1120S by the due date (or extended due date), the IRS imposes failure-to-file penalties. As of 2024, the penalty is $210 per shareholder per month, up to a maximum of 12 months. This penalty applies even if the corporation owes no tax, since S corporations are typically pass-through entities.

Additionally, late filing can delay shareholders’ ability to file their own returns because they need the Schedule K-1 issued by the corporation. The IRS may also assess interest charges on unpaid taxes related to payroll, Social Security, and Medicare if those filings are late.

To minimize exposure, S corporations should maintain a clear compliance calendar and file Form 7004 in advance of the March 15 deadline if more time is needed.

Tax Deadlines in Calendar Year 2017 for 2016 Returns

The following are important dates you should know pertaining to IRS Form 1040ES or your tax payments:

  • April 17, 2017
  • June 15, 2017
  • September 15, 2017
  • January 16, 2018

Take note of the following extensions given to certain IRS form deadlines:

  • IRS Form 1065: Partnership returns, extended to September 15, 2017 from March 15, 2017.
  • IRS Form 1041: Filing estate or trust income tax, extended to October 2, 2017 from April 17, 2017.
  • IRS Form 1120: Filing income tax returns for a C corporation, extended to October 16, 2017 from April 17, 2017. 
  • IRS Form 1120-S: S corporation returns, extended to September 15, 2017 from March 15, 2017.
  • IRS FinCEN Form 114: Reports of foreign bank accounts; the deadline is April 18, 2017.

2025 S Corp Tax Filing Deadlines and Key Dates

For the 2024 tax year (returns due in 2025), the main S corp tax filing deadline is March 17, 2025, since March 15 falls on a Saturday. Businesses filing for an extension using Form 7004 will have until September 15, 2025 to submit Form 1120S.

Additional key dates include:

  • January 31, 2025: Deadline to issue Form W-2s to employees and Form 1099s to contractors.
  • April 15, 2025: Deadline for shareholders to file individual returns and pay any associated tax.
  • June 17, 2025, and September 16, 2025: Estimated quarterly payment deadlines for shareholders.
  • October 15, 2025: Extended due date for individual returns if Form 4868 was filed.

Businesses should verify these dates each year, as weekends and federal holidays can shift the final filing deadlines.

Every Date You Need to File Your 2017 Tax Return

Corporations have a deadline to file their tax returns — Form 1065 for partnerships and Form 1120S for S corporations. This date was extended to September 17, 2018 from March 15, 2018. The deadline for Form 1120 of C corporations and Form 1040 for individuals has been extended to October 15, 2018 from April 17, 2018. Form 990 is filed by exempt organizations, and it has a deadline of August 15, 2018, an extension from May 15, 2018.

Tips for Staying Compliant and Avoiding Late Fees

To avoid late filing penalties and ensure compliance with IRS regulations, S corporations should adopt the following best practices:

  1. Mark all tax filing deadlines early — include federal, state, and local requirements.
  2. Use accounting software or a tax calendar tool to track Form 1120S, Form 7004, and payroll tax filings.
  3. Coordinate with shareholders early to prepare and distribute Schedule K-1 forms promptly.
  4. Monitor changes to IRS due dates since holiday adjustments and new legislation can shift deadlines.
  5. Consult a tax professional or attorney if your business uses a non-calendar fiscal year or operates across multiple states, as local requirements can differ.

Staying proactive and well-organized can save S corporations significant time and money during the filing season.

Frequently Asked Questions

1. What is the S corp tax filing deadline for 2025? For calendar-year corporations, the due date is March 17, 2025, since March 15 falls on a weekend.

2. Can S corporations file for an extension? Yes. File Form 7004 to receive an automatic six-month extension, moving the deadline to September 15, 2025.

3. What happens if my S corp files late? The IRS imposes a $210 per shareholder per month penalty (up to 12 months) for late filings, even if no tax is due.

4. Do S corps pay federal income taxes? No, S corporations are pass-through entities; income flows to shareholders who pay individual taxes.

5. How do holidays affect the tax filing deadline? If the deadline falls on a weekend or federal holiday, it automatically moves to the next business day.

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