Form 1120-F is unusual among business returns: its due date depends on the filer’s footprint. The same U.S.-source income reported by two foreign corporations can be due two months apart based purely on whether one maintains an office in the United States.
Here is the due-date split, the Form 7004 mechanics for each situation, and the 18-month rule that makes timely (or at least protective) filing existential for deductions.
Two due dates for one form
With a U.S. office or place of business, Form 1120-F follows the C corporation calendar: due the 15th day of the 4th month after year end (the 3rd month for June 30 fiscal years). For a calendar-year filer, that is April 15.
Without a U.S. office or place of business, the return is due the 15th day of the 6th month after year end — June 15 for a calendar year. Certain foreign corporations under Regulations section 1.6081-5 also get to both file and pay by that 6th-month date automatically, no extension request needed; they attach a statement rather than filing Form 7004 for that initial stretch, and use line 4 of Form 7004 only to request additional time.
The Form 7004 mechanics
The extension code for Form 1120-F is 15 on Part I, line 1. A foreign corporation with no U.S. office also checks the box on line 2 — the instructions describe it as the box for "a foreign corporation that does not have an office or place of business in the United States" — and files the 7004 by its 6th-month due date.
The extension runs 6 months from the applicable due date. And the universal rule applies verbatim: "Form 7004 does not extend the time to pay any tax due." Estimated tax and balance-due mechanics run from the original deadline, with interest accruing from that date on any shortfall.
File a separate Form 7004 for each return. A foreign corporation with multiple filing obligations (say, Form 1120-F and Form 8804 as a partner-withholding agent) extends each one individually.
The 18-month rule: why late means losing deductions
For most filers a late return means penalties. For a foreign corporation it can mean something worse: Form 1120-F must generally be filed on time — within 18 months of the due date under the applicable regulations — for the corporation to claim deductions and credits against its effectively connected income. Blow past the window and the IRS can tax gross income, deductions disallowed.
That is why foreign corporations unsure whether they even have a U.S. filing obligation often file protectively — and why extending with Form 7004 (rather than simply filing late) matters more here than almost anywhere else in the corporate system.
Frequently asked questions
When is Form 1120-F due?⌄
Which Form 7004 code extends Form 1120-F?⌄
Does the extension extend the time to pay?⌄
What is the 18-month rule?⌄
Related guides
More in Business Tax Extensions (Form 7004)
Official sources
Tax rules, rates and deadlines change — verify current requirements against the IRS sources above before acting. This guide is general information, not tax or legal advice.