Tax Extension DeadlineStart with the election
The company folder is open, and the household return is a different night. The business application is one form. The day it has to be in depends on the return the entity files, not on the word in its name.
Confirm the entity dayWho files it
Partnerships file it for Form 1065. S corps file it for Form 1120-S. C corps file it for Form 1120. The form is one application with a code for the return you are extending, and it has to be in by that return's original due date. For a calendar year, the partnership and the S corp start in the middle of March and land in the middle of September if extended. The C corp starts in the middle of April and lands in the middle of October. A fiscal year uses the same gap, counted from its own year end.
Those ordinary dates are on the IRS page about Form 7004 and on the extension page that points business filers there. When that original due date falls on a weekend or a federal holiday, Form 7004 follows the next weekday the IRS page names for the year. We do not print a private calendar that disagrees with those pages.
The split owners skip
An entity with two or more owners and no election on file is generally a partnership. An entity with one owner and no election is generally disregarded, and the activity rides on the owner's personal return, which means Form 4868 rather than Form 7004. An S election puts the company on the March calendar and still leaves each owner needing a personal extension. A C election puts it on the April calendar.
The acceptance letter, or the form that made the entity a corporation, is the document. A name on a bank account is not. If the letter cannot be found, the work starts by looking it up rather than by guessing March.
What the form does not carry
Form 7004 does not extend the owner's personal return. It does not extend estimated payments. It does not extend a state report that uses its own form. Owners who file only the company form and then feel finished have left the personal return and the next estimate sitting in the open. The year's page puts those rows on one list so the company form is not asked to do three jobs.