Form 1120-F is due on the 15th day of the fourth month after the close of the tax year if the foreign corporation has an office or place of business in the United States, which lands on April 15 for calendar-year filers. A foreign corporation without a U.S. office gets two extra months and files by the 15th day of the sixth month after year-end, or June 15 for calendar-year filers.1Internal Revenue Service. Instructions for Form 1120-F Both deadlines shift to the next business day when they fall on a Saturday, Sunday, or legal holiday, and a six-month extension is available. Missing the deadline without a protective return on file can permanently strip the corporation’s right to claim deductions and credits against its U.S. income.
The Two Standard Deadlines
A single factor determines which deadline applies: whether the foreign corporation has an office or place of business in the United States during the tax year.
- With a U.S. office or place of business, the return is due the 15th day of the fourth month after the tax year ends. Calendar-year filers file by April 15.1Internal Revenue Service. Instructions for Form 1120-F
- Without a U.S. office, the return is due the 15th day of the sixth month after year-end. Calendar-year filers file by June 15.1Internal Revenue Service. Instructions for Form 1120-F
One important wrinkle applies to fiscal-year filers with a June 30 year-end. Those corporations file by the 15th day of the third month after year-end, which puts the deadline at September 15. Any short tax year ending in June follows the same accelerated schedule.2Internal Revenue Service. Instructions for Form 1120-F
Weekend and holiday rolls work the way they do for other federal returns: if the statutory date falls on a Saturday, Sunday, or legal holiday, the filing is timely on the next business day.
Getting an Extension
A foreign corporation that can’t finish the return by its original due date can request an automatic six-month extension by filing Form 7004 on or before that date.3Internal Revenue Service. About Form 7004 A calendar-year corporation with a U.S. office files Form 7004 by April 15 to extend the return to October 15. A calendar-year corporation without a U.S. office files Form 7004 by June 15 to extend to December 15.4Internal Revenue Service. Instructions for Form 7004
The extension only moves the filing deadline. It does not move the payment deadline. The corporation still has to estimate its tax and send the full amount by the original due date. A Form 7004 submitted without a payment leaves late-payment penalties and interest running on the unpaid balance.
When the Tax Itself Is Due
A foreign corporation that expects to owe $500 or more in U.S. income tax for the year must make quarterly estimated payments. The installments are due on the 15th day of the fourth, sixth, ninth, and twelfth months of the tax year, which for a calendar-year filer means April 15, June 15, September 15, and December 15.1Internal Revenue Service. Instructions for Form 1120-F Each payment typically covers 25% of the expected annual liability. Underpaying an earlier installment can trigger an underpayment penalty even if a later installment makes up the shortfall, because the penalty is calculated for each period separately.5Internal Revenue Service. Underpayment of Estimated Tax by Corporations Penalty
Corporations with a U.S. office must pay through the Electronic Federal Tax Payment System (EFTPS). Those without a U.S. office can use EFTPS if they have a U.S. bank account, arrange a same-day wire through a financial institution, or pay by check or money order.1Internal Revenue Service. Instructions for Form 1120-F
One category sits outside the quarterly schedule. The branch profits tax, a 30% tax on the dividend equivalent amount reported on Section III of the return,6Office of the Law Revision Counsel. 26 USC 884 – Branch Profits Tax isn’t subject to estimated payments and is settled when the return is filed.1Internal Revenue Service. Instructions for Form 1120-F
Why a Missed Deadline Can Cost More Than the Penalties
The sharpest consequence of filing late isn’t a dollar penalty. It’s the loss of deductions. A foreign corporation is only allowed to claim deductions and credits against its effectively connected income if it files a true and accurate return.7Office of the Law Revision Counsel. 26 USC 882 – Tax on Income of Foreign Corporations Connected With United States Business The regulations require that return to be filed on time to preserve those benefits.8eCFR. 26 CFR 1.882-4 – Allowance of Deductions and Credits to Foreign Corporations Without a timely return, the IRS can tax the corporation on gross income, with no offsets for expenses.
A corporation uncertain whether it has a U.S. filing obligation can preserve its deduction rights by filing a protective return. The protective return is a placeholder; it doesn’t need to contain final numbers, and it leaves the door open to amend later with actual figures. The regulations generally give a corporation 18 months after the original due date to get a protective return on file. Miss that window too, and the deductions and credits are permanently lost.
For any foreign corporation that is close to the line on whether it has effectively connected income, a protective return is cheap insurance against being taxed on gross receipts.
Late-Filing and Late-Payment Penalties
The IRS runs two separate penalty clocks, and they can both run at the same time.
- Failure to file: 5% of the unpaid tax for each month or part of a month the return is late, capped at 25%. If the return is more than 60 days late, the minimum penalty for returns due in 2026 is the lesser of $525 or 100% of the tax owed.9Internal Revenue Service. Failure to File Penalty10Internal Revenue Service. Topic No. 653, IRS Notices and Bills, Penalties and Interest Charges
- Failure to pay: 0.5% of the unpaid tax per month, also capped at 25%. The rate climbs to 1% per month if the tax remains unpaid 10 days after the IRS issues a notice of intent to levy.10Internal Revenue Service. Topic No. 653, IRS Notices and Bills, Penalties and Interest Charges
When both apply in the same month, the failure-to-file penalty is reduced by the failure-to-pay amount for that month. The filing penalty maxes out after five months; the payment penalty keeps running until the balance is cleared.9Internal Revenue Service. Failure to File Penalty
Interest accrues on top of both penalties and compounds. The IRS resets its underpayment rate quarterly; the corporate underpayment rate is 7% for the first quarter of 2026 and 6% for the second quarter.11Internal Revenue Service. Quarterly Interest Rates Interest runs from the original due date until the balance is paid, no matter whether a filing extension was granted.
Treaty Positions Have Their Own Disclosure Deadline
If the return takes any treaty-based position, such as claiming a reduced branch profits rate or exempting an item of income under a tax treaty, Form 8833 must be attached when the return is filed.12Internal Revenue Service. About Form 8833, Treaty-Based Return Position Disclosure Under Section 6114 or 7701(b)13Office of the Law Revision Counsel. 26 USC 6114 – Treaty-Based Return Positions Each undisclosed position carries a $10,000 penalty for a C corporation, counted separately.14Office of the Law Revision Counsel. 26 USC 6712 – Failure to Disclose Treaty-Based Return Positions A return claiming several treaty benefits without the required Form 8833 can generate several of those penalties at once.