An S corporation extends Form 1120-S by filing Form 7004 with form code 25 by March 15 (for calendar-year corporations). The extension runs six months, to September 15. It is automatic and the corporation does not have to state a reason.
Why March and not April
S corporations pass their income through to shareholders on Schedule K-1. The shareholders need those K-1s to file their own returns in April, so the entity return is due a month earlier.
The penalty for filing late
The S corporation usually owes no federal income tax itself, but the late filing penalty is not tied to tax. It is a flat amount per shareholder per month, for up to twelve months. For returns due in 2026 the amount was $255 per shareholder per month, indexed annually. A three-shareholder company that files four months late owes about $3,060. The penalty applies whether the return is filed late or filed on time without the required K-1 information.
What the extension does for shareholders
Nothing. Each shareholder's Form 1040 is still due April 15 and each must file their own Form 4868 if the K-1 will not arrive in time. Tell them in March.
Fiscal years
An S corporation with a permitted fiscal year files by the 15th day of the third month after year end and extends six months from there.
Common mistake
An LLC that elected S status and still thinks of itself as a partnership files code 09. The extension attaches to a Form 1065 the entity does not file, and the 1120-S is late.
Ready to file it?
You can file a business extension (Form 7004) online in a few minutes with TaxExtension.com, an IRS-authorized e-file provider operated by our publisher. The extension is automatic; the payment is still due on the original date.
Sources
- IRS, About Form 7004
- IRS, Instructions for Form 1120-S, late filing penalty
- IRS, Failure to file penalty