The S-Corp return is due March 15
Form 1120-S is due March 15 for a calendar-year S-Corp, or the next business day. You can get six more months by filing Form 7004 before the deadline. Filing late brings a penalty for each shareholder, each month, even when the company owes no tax, so don't skip it.
Updated November 2026 · By Pankil Kumar, Managing Partner
Quick facts
- Due. March 15 for calendar-year S-Corps
- Extension. Six more months, to September 15
- Late penalty. Per shareholder, per month, up to 12 months
Why is it due a month before your personal return?
An S-Corp doesn't usually pay income tax itself. It reports its profit on Form 1120-S and passes each owner's share out on a Schedule K-1. Owners need that K-1 to file their own Form 1040 by April 15, so the company files first.
What does a late Form 1120-S cost?
The penalty is charged for each month or part of a month the return is late, for each shareholder, for up to 12 months. So a two-owner company that's six months late pays it twelve times, even with zero tax due. The dollar amount adjusts with inflation, and the Form 1120-S instructions list the current figure.
The IRS may waive it for reasonable cause, and some small corporations have other relief options. Still, an extension costs nothing and takes minutes.
How do you extend it?
File Form 7004 by March 15. That moves the filing deadline to September 15. It doesn't give any extra time for the owners' personal tax payments. If you expect to owe on your Form 1040, you still pay by April 15. Here's how extensions work.
What do you need to file?
- Clean, reconciled books for the full year
- Payroll reports that tie to your W-2s and Forms 941
- Records of owner salary, distributions and loans
- Prior year return, including balance sheet
- Fixed asset purchases and sales
- Each owner's stock and debt basis, if tracked
Owners who forget a salary create a real problem, since the IRS expects reasonable pay before distributions.
What about state returns?
Most states with an income tax want an S-Corp return too, and rules vary. Some states charge an entity-level tax or fee, like California's 1.5% tax. If your company works in several states, you may need more than one return, and possibly K-1 equivalents for each owner.
What if you're already late?
File as soon as you can. The penalty runs monthly, so each month you save counts. Send K-1s to owners right away so they can file or amend, then ask whether penalty relief applies. See what to do about a late business return.
Sources
General information, not tax advice for your situation.
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See our business tax returns serviceDoes an S-Corp have to file if it had no income?
Yes. An S-Corp generally files Form 1120-S every year, even with no income, until it's formally closed.
Can I file my S-Corp return after my personal return?
Not if you need the K-1 figures. File an extension for your personal return, and pay any tax you expect by April 15.
When is the S-Corp extended deadline?
September 15 for calendar-year companies, or the next business day, if Form 7004 was filed on time.
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