IRS Form 1120-S Due Dates
E-File your IRS Form 1120-S for the 2025 tax year by March 16, 2026, to meet federal S corporation filing deadlines and avoid potential penalties.
Staying compliant with the IRS requires more than just filling out forms - it requires filing them on time. For S corporations, the annual return is filed using Form 1120-S, and its due date is much earlier than many business owners expect.
Missing the deadline doesn’t just bring financial penalties; it can also create headaches for your shareholders, who rely on timely Schedule K-1s to complete their personal tax filings. That’s why understanding the 1120-S due date for 2026 is critical.
Table of Contents
When is Form 1120-S Due?
The following table lists the standard due dates for filing Form 1120-S. Calendar-year filers have a deadline in March that never changes. Fiscal-year filers, however, must file by the 15th day of the 3rd month after the close of their tax year.
| S Corporation Type | Tax Year End | Form 1120-S Due Date |
|---|---|---|
| Calendar-Year S Corporation | December 31, 2025 | March 16, 2026 |
| Fiscal-Year S Corporation | Last day of fiscal year | 15th day of the 3rd month after the tax year ends |
Why the 1120-S Deadline Exists
The IRS sets an early deadline for S corporations because of how these businesses are structured. Unlike C corporations, S corporations are pass-through entities. This means:
- The corporation itself doesn’t generally pay income tax.
- Instead, profits and losses “pass through” to shareholders, who report them on their personal tax returns.
- To do this, the corporation must issue Schedule K-1s to shareholders — and those K-1s come from Form 1120-S.
If the IRS allowed S corporations to file at the same time as individuals (April 15), shareholders wouldn’t have enough time to report their share of income. That’s why the deadline falls in
mid-March, giving shareholders a buffer before their April 15 filing deadline.
Extension Due Date
If your S corporation requires more time to E-file Form 1120-S, you can get an automatic 6-month extension by filing Form 7004 by the original due date. The extension offers you extra time to file your return, but it does not extend the time to pay any taxes owed.
| S Corporation Type | Original Due Date | Extension Due Date |
|---|---|---|
| Calendar-Year S Corp | March 16, 2026 | September 15, 2026 |
| Fiscal-Year S Corp | 15th day of the 3rd month after tax year-end | 6 months after the original due date |
Example: If you have a fiscal year ending June 30, 2026, your Form 1120-S is due on September 15, 2026. The extended filing date is March 15, 2027, when you file Form 7004.
Key Points to Remember
- To receive an extension, file Form 7004 by the original due date. This extension applies only to filing taxes, not to payments.
- You can avoid penalties and interest by paying any corporate-level taxes due by the original due date.
- You may still owe tax such as Built-in Gains Tax, Excess Net Passive Income Tax, and any other corporate taxes that may apply.
Penalties for Late Filing or Payment
The IRS enforces strict late-filing penalties for S corporations.
- Late-Filing Penalty: $245 per shareholder per month, up to 12 months, even if no tax is owed.
- Late-Payment Penalty: If your S corporation owes taxes, 5% of unpaid tax per month applies (first month: smaller of $510 or unpaid tax).
Examples:
- 2 shareholders, 3 months late → $245 × 2 × 3 = $1,470 (late-filing).
- 5 shareholders, 6 months late, plus $10,000 unpaid tax → late-filing + 5% of unpaid tax per month (late-payment).
Even if the S corporation has no income or owes no tax, penalties still apply if the return is late.
State Filing Deadlines
In addition to the federal IRS deadline, many states require S corporations to file separate state-level returns. Deadlines vary:
- Some states (e.g., California, New York) align with the federal due date.
- Others set their own filing deadlines.
- States may also have their own penalties for late filing, separate from IRS penalties.
Always check with your state’s Department of Revenue or Franchise Tax Board.
Best Practices to Avoid Missing the Deadline
- Use a tax calendar – Mark March 16, and September 15(if extended).
- Prepare early – Gather financials right after year-end to avoid last-minute rush.
- Distribute K-1s early – Shareholders need these forms to report their share of income on personal tax returns by the April 15 deadline.
- File electronically – E-filing reduces errors and provides instant confirmation.
- Set reminders – Use accounting software or digital reminders to track key dates.
- Consult professionals – If your business has complex operations, ensure you get expert help early.
Frequently Asked Questions (FAQs)
1. What happens if my S corporation had no activity in 2025?
You must still file Form 1120-S by March 16, 2026. The IRS requires an annual return even if there was no income, expense, or activity.
2. Can I avoid penalties by filing late if I extend shareholder 1040 returns?
No. The corporation and the shareholder returns are separate. Late 1120-S filing triggers corporate penalties regardless of shareholder extensions.
3. If I file Form 7004, do I get more time to pay taxes?
No. Form 7004 only extends the filing deadline. Any tax liability is still due by the original deadline.
4. How can shareholders be affected by a late 1120-S filing?
Shareholders may be forced to extend their personal returns if K-1s are delayed, which can disrupt their tax planning and refunds.
5. Does every state follow the March deadline?
Not always. Some states have different due dates for corporate returns. For example, New York requires an S corporation return (Form CT-3-S), and deadlines may differ.
6. What if I miss both the original and extended deadlines?
If you miss both deadlines, the IRS will impose the maximum late-filing penalty (12 months × $245 × number of shareholders). If your S corporation owes taxes, a late-payment penalty of 5% per month may also apply. Missing deadlines may also increase your risk of audit.
Don’t Risk Missing the Deadline
The S corporation filing deadline is earlier than most expect — and the penalties are step if you miss it. Preparing
ahead ensures your business stays compliant and your shareholders can file smoothly.
Avoid costly penalties
