Form 1120-S is the yearly tax return for an S corporation, filed by any business that elected S status on Form 2553 and had it accepted. It's due by the 15th day of the 3rd month after the tax year ends, which was March 16, 2026 for calendar year 2025, and a late return costs $255 for each month late, multiplied by the number of shareholders, even when no tax is due.
That penalty is easy to underestimate. Profit passes through to shareholders on their K-1s, so the company itself often owes little or no tax, and it's tempting to assume a late return costs nothing. It doesn't work that way.
Who files Form 1120-S
A corporation or other entity must file Form 1120-S if it elected S corporation status by filing Form 2553, the IRS accepted the election, and the election is still in effect. The IRS says not to file Form 1120-S unless you've filed, or are attaching, Form 2553. If you haven't heard back within 2 months of filing Form 2553, follow up with the IRS.
That includes an LLC that elected S status. If you're still deciding whether that election makes sense, this S corp vs LLC comparison walks through the trade off.
Key dates and penalties
| Item | Rule (2025 instructions) |
|---|---|
| Due date | 15th day of the 3rd month after the tax year ends; March 16, 2026 for calendar year 2025 |
| Extension | File Form 7004 by the regular due date |
| Schedule K-1s to shareholders | By the day the return is due |
| Late filing, no tax due | $255 per month or part month, up to 12 months, times the number of shareholders |
| Late filing, tax due | That amount plus 5% of the unpaid tax per month, up to 25% |
| Returns more than 60 days late (filed in 2026) | Minimum of the smaller of the tax due or $525 |
| Late payment | Half of 1% of unpaid tax per month, up to 25% |
| Missing or wrong Schedule K-1 | Up to $340 per K-1 |
Those figures are from the 2025 instructions, the latest edition as of October 2026, so check the next edition before filing a 2026 return. Here's what the shareholder multiplier means in practice: a three-shareholder S corp that files four months late with no tax due faces $255 for each of the four months, for each of the three shareholders: twelve lots of $255.
What goes on the return
- Income and deductions on page 1, including line 7 for officer compensation and line 8 for other salaries and wages.
- Schedule K, the totals of income, deductions and credits passed through to shareholders.
- A Schedule K-1 for every person who was a shareholder at any time in the year, showing their separate share. Attach a copy to the return and give each shareholder theirs, with the shareholder instructions.
- Form 1125-E, Compensation of Officers, if total receipts are $500,000 or more; the line 7 figure then comes from that form.
- Any company-level taxes that can still arise, such as the built-in gains tax or the excess net passive income tax. If those total $500 or more, estimated payments are generally required.
Officer pay: the reasonable compensation rule
The instructions are plain: distributions and other payments to a corporate officer must be treated as wages to the extent they're reasonable compensation for services. Taking everything as distributions to avoid payroll tax isn't what the rules allow. Pay a reasonable salary through payroll first, then take distributions.
It matters for your personal tax too. The qualified business income deduction interacts with how the S corp pays you; the QBI deduction explained covers that.
A quick filing checklist
- Confirm the IRS accepted your Form 2553 before you file the first 1120-S.
- Run payroll for officers who work in the business, so line 7 reflects reasonable compensation.
- Prepare a K-1 for everyone who held shares at any point in the year, not just at year end.
- Diary the 15th day of the 3rd month, and file Form 7004 before it if you need more time.
E-filing and the 10-return rule
For returns filed on or after January 1, 2024, S corporations must e-file Form 1120-S if they file 10 or more returns of any type in the calendar year, counting income tax, employment tax, excise tax and information returns together. A small company with a handful of W-2s and 1099s can reach that quickly. The IRS can waive the requirement for hardship, but you have to ask in writing.
Losing S status
Once made, the election stays until it's terminated. It can be revoked with consent from shareholders holding more than 50% of the shares. It also ends automatically if, for 3 consecutive years, the company has accumulated earnings and profits and more than 25% of its gross receipts are passive investment income. After a termination, you generally need IRS consent to re-elect before the fifth tax year.
The verdict
Form 1120-S is mostly an information return, but treat its deadline as seriously as any tax bill. The $255 per shareholder per month penalty applies even when the company owes nothing, so file Form 7004 by the due date if you're not ready. Get the K-1s out on time, because your shareholders can't file without them. And pay yourself a reasonable salary through payroll: it's the rule the IRS states most plainly, and the one with the most at stake.
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Frequently asked questions
Who has to file Form 1120-S?
Any corporation or other entity that elected S corporation status on Form 2553, had the election accepted, and still has it in effect.
When is Form 1120-S due?
By the 15th day of the 3rd month after the tax year ends. For calendar year 2025 it was March 16, 2026, because March 15 fell on a Sunday.
What is the penalty for filing Form 1120-S late?
For returns with no tax due, $255 for each month or part month late, up to 12 months, multiplied by the number of shareholders.
How do I get an extension for Form 1120-S?
File Form 7004 by the regular due date of the return.
When do shareholders get their Schedule K-1?
The corporation must give each shareholder a Schedule K-1 by the day Form 1120-S is required to be filed.
Is e-filing required for Form 1120-S?
Yes, if the S corporation files 10 or more returns of any type in the calendar year, including employment and information returns.
Can an S corporation owner take only distributions?
No. The IRS says payments to an officer must be treated as wages to the extent they're reasonable compensation for services.
