Form 1120-S: The S Corporation Return, Who Files It, and When
Published November 7, 2026
Form 1120-S is the income tax return for an S corporation. The 2025 Instructions for Form 1120-S describe who must file it. They also cover how the S election can end, when the return is due, and what shareholders receive. This post is general information. It does not replace the instructions.
Who must file
A corporation or other entity must file Form 1120-S in three cases. It elected S status by filing Form 2553. The IRS accepted the election. And the election is still in effect.
Do not file Form 1120-S for a tax year before the year the election takes effect.
If no notice of acceptance arrives within 2 months after filing Form 2553, follow up with the IRS. If box Q1 was checked to ask for a letter ruling, the wait is 5 months. A late election may qualify for relief. The Instructions for Form 2553 explain how to ask for it.
When the election ends
Once made, the S election stays in effect until it is terminated. The instructions list three ways this happens.
- The corporation is no longer a small business corporation under section 1361(b). The termination starts the day it stops meeting that requirement.
- For 3 consecutive tax years, the corporation has accumulated earnings and profits. It also gets more than 25% of its gross receipts from passive investment income. The election ends on the first day of the next tax year.
- The election is revoked with the consent of shareholders who hold more than 50% of the outstanding shares.
After a termination, the corporation generally needs IRS consent to elect again. That consent covers tax years before the fifth tax year after the first year the termination took effect.
When the return is due
An S corporation generally files Form 1120-S by the 15th day of the 3rd month after its tax year ends. For a calendar-year corporation, the instructions say the 2025 return was due March 16, 2026. March 15 fell on a Sunday that year.
A dissolved corporation generally files by the 15th day of the 3rd month after the date it dissolved.
A corporation that needs more time can request an automatic extension on Form 7004 by the regular due date.
Schedule K-1 and the shareholders
The corporation's income, losses, deductions, and credits generally pass through to its shareholders. The passive activity rules apply to each shareholder's share. Each shareholder decides for themselves whether they materially participated in an activity.
The corporation reports each share on a Schedule K-1 (Form 1120-S). The shareholder uses that schedule on the personal return. Questions about basis are covered in Form 7203: S Corporation Stock and Debt Basis.
How it differs from other returns
An S corporation is a pass-through entity. Its return reports the business results. The tax on that income generally falls on the shareholders. A partnership files a different return. See Partnership returns: what Form 1065 reports.
Individuals who need more time use Form 4868. That form is covered in Form 4868: More Time to File, Not to Pay. Businesses request extensions on Form 7004.
Common questions
Do shareholders file the corporation's return? No. The corporation files Form 1120-S. Each shareholder uses the Schedule K-1 on the shareholder's own return.
What if the return is late? Late filing can bring a penalty. Check the late filing section of the instructions.
Does the election last forever? It does not. The termination rules described above can end it. In some cases a new election needs IRS consent.
Checklist
- Confirm the S election was accepted and is still in effect.
- Note the due date: the 15th day of the 3rd month after the tax year ends.
- Prepare a Schedule K-1 for each shareholder.
- Keep the records that support basis and each shareholder's share.
Sources: Sources: IRS, Instructions for Form 1120-S (2025), U.S. Income Tax Return for an S Corporation (https://www.irs.gov/pub/irs-pdf/i1120s.pdf) This is general information, not advice about your specific return.
