You took the extension thinking there was time. Now it’s almost September.
If your S Corporation took the extension back in March, you have until September 15, 2025, to file Form 1120-S.
This S Corp filing deadline 2025 is the last opportunity to file without penalties and ensure your tax status and shareholder records remain in order.
There’s still time to file accurately and avoid any last-minute issues or unnecessary attention from the IRS.
This guide provides a complete overview to help you meet your obligations before the S Corp filing deadline 2025. It includes key dates, required forms, IRS trends, and actionable tips to ensure timely and accurate filing of Form 1120-S.
What Is an S Corporation and Why Filing Matters
An S Corporation is a business structure that offers two main benefits: it protects the personal assets of its owners and avoids double taxation. In an S Corporation, income tax is not paid at the corporate level. Instead, the profits and losses pass through to the owners, who report them on their personal tax returns.
Filing Form 1120-S on time is important because it keeps your S Corporation in good standing with the IRS. It also ensures accurate reporting for shareholders and helps you avoid late fees, penalties, or complications that could affect your tax status.
This tax structure avoids double taxation but comes with ongoing responsibilities. Even though the S Corporation doesn’t pay income tax itself, it must still file tax documents with the IRS. It also gives each shareholder a Schedule K-1, which shows how much profit or loss they got from the company. Shareholders use this form to report income on their individual tax returns.
Failing to complete these steps on time may cause your business to miss the S Corp filing deadline 2025, leading to penalties and added pressure.
Non-compliance with these obligations may result in significant consequences, such as:
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• Late filing penalties
• Disruption of shareholder tax reporting
• Risk of losing S Corporation status and reverting to a C Corporation
Original IRS Filing Deadline: March 17, 2025
Typically, S Corporations following a calendar year must file their federal return by March 15. Because March 15, 2025, falls on a Saturday, the filing deadline is automatically extended to Monday, March 17, 2025.
By this date, S Corporations should have:
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• Filed Form 1120-S with the IRS
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• Distributed Schedule K-1 to each shareholder
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• Filed Form 7004 if more time was needed
Missing the filing deadline without an approved extension can result in IRS penalties of $235 per shareholder for each month it’s late, capped at 12 months.
The earlier you begin preparing for the S Corp filing deadline 2025, the smoother your filing process will be.
Extended Deadline: September 15, 2025
If your business filed Form 7004 before the March 17 deadline, you were granted an automatic six-month extension, making September 15, 2025, the final due date for submitting Form 1120-S for tax year 2024.
This S Corporation filing deadline 2025 applies only to filing not to payment. Shareholders are still expected to pay any tax due on time.
Key reminders:
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• This extension only delays the filing, not the payment. Shareholders are still expected to pay taxes on their share of the income as originally scheduled.
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• All Schedule K-1s must be issued promptly after filing to avoid disrupting shareholder’s tax reporting.
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• Late filing beyond this date can lead to additional penalties and may affect shareholder tax compliance.
Preparing in advance can help avoid last-minute complications, especially if your business has complex financials or multiple shareholders.
What Documents Do You Need to File?
To stay compliant, S Corporations must file several key forms:
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• Form 1120-S – reports income, deductions, credits, and distributions
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• Schedule K-1 – shows each shareholder’s share of income for personal tax filing
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• Form 7004 – extension request form
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• Form 2553 – used to elect S Corporation status for new businesses
Depending on the business structure, additional schedules like B, L, M-1, and M-2 may also be required. Ensuring these are accurate and submitted ahead of the S Corp filing deadline 2025 will help maintain good standing with the IRS.
If you’re confused about Form 1065 vs Form 1120-S, you’re not alone. Both are used bypass-through entities, but they apply to different structures; Form 1065 is for partnerships, while Form 1120-S is for S Corporations. Both generate Schedule K-1s for their respective partners or shareholders, but the filing obligations and structures they apply to are distinct.
Form 2553: Electing S Corporation Status
New businesses that want to operate as S Corporations must file Form 2553 with the IRS. This form is essential for gaining S Corp treatment and must be filed within 2 months and 15 days of the beginning of the tax year the election is intended to take effect.
Businesses that miss the deadline may apply for late election relief under Revenue Procedure 2013-30, if they meet IRS requirements.
Filing Options: E-File vs. Paper Submission
The IRS provides two options for submitting your S Corporation tax return:
1. Electronic Filing
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• Faster and more secure
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• Provides real-time confirmation
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• Reduces the risk of common filing errors
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• File Form 1120-S securely using IRS-authorized e-file providers.
2. Paper Filing
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• Must be mailed to the appropriate IRS address listed in the Form 1120-S instructions.
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• Takes longer to process and lacks instant confirmation.
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• Higher chance of processing delays during peak tax season.
Given the importance of timely filing, e-filing is strongly recommended, especially if you’re approaching a deadline.
Don’t Overlook State Filing Requirements
Many states require businesses to file returns or pay annual franchise taxes, even if federal taxes are not due. Some states also require a separate S Corporation election, such as:
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• California
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• New York
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• New Jersey
Check your local Department of Revenue or use the state tax agency list. Some state deadlines may not align with the federal S Corp filing deadline 2025, so be sure to verify both timelines.
IRS Trend in 2025: Increased Scrutiny on S Corps
One of the most important changes in 2025 is the IRS’s renewed focus on S Corporation compliance. The agency has launched targeted campaigns aimed at identifying:
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• S Corps that fail to pay reasonable compensation to shareholder-employees
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• Incomplete or delayed Schedule K-1 filings
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• Repeated late or inaccurate Form 1120-S submissions
The S Corp filing deadline 2025 is no longer just a due date, it’s part of a broader compliance landscape. Late, inaccurate, or incomplete filings can increase the likelihood of being audited or penalized.
More information is available via the IRS Compliance Campaigns page and their guidelines on S Corporations.
Common Mistakes to Avoid
Here are common errors before the S Corp filing deadline 2025 that can be easily avoided with proper planning:
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• Missing the September 15 deadline
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• Not issuing K-1s to all shareholders on time
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• Assuming the extension covers tax payment (it doesn’t)
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• Forgetting state-specific obligations or deadlines
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• Misclassifying shareholder compensation
Even one mistake can trigger IRS correspondence or penalties, so it’s important to double-check.
Best Practices to Stay Compliant
To stay compliant and meet the S Corp filing deadline 2025, consider the following:
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• Mark important dates and set reminders
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• Begin document preparation by early August to avoid delays
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• Collaborate with an experienced CPA or a reliable tax advisor for expert guidance
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• Use cloud-based or AI-powered accounting software for accuracy
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• Distribute K-1s well in advance of shareholder filing deadlines
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• Use the IRS Business Tax Account for digital access and updates
A proactive approach helps reduce filing stress and positions your business for long-term stability.
Conclusion
The S Corp filing deadline 2025 is more than just a calendar date, it’s a crucial compliance checkpoint that keeps your corporation in good standing, ensures accurate shareholder reporting, and helps you avoid unwanted IRS attention.
Make sure your documents are in order, your forms are ready, and your shareholders are informed. Avoid unnecessary penalties by filing early and leaning on expert support where needed.
Need help filing your S Corp return or managing compliance deadlines?
Book a free consultation with us to ensure you’re ready well before the S Corp filing deadline 2025 arrives.
