Foreign Corporation (1120-F) vs Foreign-Owned LLC (5472 + Pro-Forma 1120): Which US Tax Regime Applies

The single most common point of confusion for cross-border founders is treating Form 1120-F and the Form 5472 + pro forma 1120 package as interchangeable. They are not. They answer different questions, sit on different parts of the Code, and produce different bills.

Form 1120-F is an income tax return. It is the return of the foreign corporation itself — a non-US entity that earns US income or operates in the United States. It computes and pays actual US tax, transmits treaty disclosures on Form 8833, and is where the branch profits tax under section 884 is calculated.

Form 5472 + pro forma 1120 is an information report. A US single-member LLC owned by a foreign person is generally disregarded for income tax purposes, but Treasury regulations treat it as a domestic corporation solely for the section 6038A information-reporting rules. That is why a foreign-owned disregarded LLC files a near-blank pro forma Form 1120 with Form 5472 attached to disclose reportable transactions with its foreign owner — but it is not paying entity-level income tax on that return.

So the threshold question is not which form you would rather file. It is a facts question: what is the legal entity (a foreign corporation, or a US LLC), and what is it doing in the United States. The rest of this guide walks the two trigger tests, the case where both fire at once, the two tax buckets, the branch-level second tax, protective filing, treaty/PE analysis, and the conversion trade-offs.

The IRS instructions cast the Form 1120-F net wider than most expect. A foreign corporation generally must file if, during the tax year, it was engaged in a trade or business in the United States — whether or not it had US-source income from that business, and whether or not that income is exempt under a treaty.

It must also file if it had income, gains, or losses treated as effectively connected with a US trade or business (ECI), or if it was not engaged in a US trade or business but had US-source income for which its US tax liability was not fully satisfied by chapter 3 withholding. The same return is used to claim refunds of over-withheld tax, to transmit a Form 8833 treaty-based position, and to compute the branch profits tax.

Two practical implications fall out of that wording. First, a treaty position does not remove the filing obligation — a corporation that concludes a treaty zeroes out its US tax is still expected to file (see protective filing in section 7). Second, even a corporation with only passive US-source income can land in 1120-F territory if its withholding did not fully cover the tax — for example, where the wrong rate was applied or a payment slipped through under-withheld.

The other path applies to a very different taxpayer: a US single-member LLC owned by a foreign person. Because the LLC is disregarded for income tax, it has no income tax return of its own — but section 6038A and its regulations treat it as a domestic corporation solely for information reporting, requiring it to file Form 5472 attached to a pro forma Form 1120 to disclose reportable transactions with its foreign owner and related parties.

This guide does not re-walk that mechanics — the package, the Ogden mailing/fax procedure, zero-activity edge cases, and the $25,000 penalty are already covered in our existing guides. The point to hold here is simply the contrast: the LLC filing is an information return that computes no income tax, while Form 1120-F is the income tax return of a foreign corporation. Mixing them up is the root of most of the confusion this guide exists to resolve.

Here is the case the two-regime framing usually misses: the regimes are not mutually exclusive. If a foreign corporation owns a US disregarded LLC, both filings can be required at once.

At the LLC level, the disregarded LLC may have a Form 5472 + pro forma 1120 obligation under section 6038A, exactly as it would if any foreign person owned it. At the owner level, the foreign corporation may separately owe Form 1120-F — for instance, if it is engaged in a US trade or business through that LLC, or has US-source income not fully satisfied by withholding. The disregarded-entity rules collapse the LLC for income-tax purposes, but they do not eliminate the corporation's own Form 1120-F analysis.

In other words, the LLC's information report and the corporation's income tax return live on different rails and can both run. A foreign corporate owner who files only the 5472 package, assuming it has "handled" its US filing, can be sitting on an unfiled 1120-F — and, with it, the protective-filing and deduction-preservation risks discussed below.

Once a foreign corporation is inside the 1120-F regime, the Code splits its US income into two buckets that are taxed in fundamentally different ways.

Section 881 — 30% gross-basis tax on FDAP. Certain US-source income that is not connected with a US business — broadly fixed or determinable annual or periodical income such as dividends, interest, rents, and royalties — is taxed at a flat 30% on the gross amount, with no deductions. This is normally collected through the chapter 3 withholding system and reported by the withholding agent on Form 1042-S, and a treaty can lower the 30% rate. On the return, this is the Section I computation, which the form tells you not to use for amounts already properly withheld and reported on Form 1042-S.

Section 882 — net-basis tax on ECI. Income that is effectively connected with a US trade or business is taxed on a net basis — gross ECI minus properly allocable deductions — at the same 21% corporate rate as a domestic corporation. This is the Section II computation, where allocated deductions (Schedule H) and allocated interest expense (Schedule I) come in and Schedule J computes the tax. Section 894 requires all of this to be applied with due regard to US treaty obligations.

The gulf between the two buckets — 30% of gross with no deductions versus 21% of net — is why the engaged-in-a-US-trade-or-business and effectively-connected questions are the most consequential determinations on the whole return.

Section 884 is what makes operating a US business directly through a foreign corporation's branch economically different from operating it through a US subsidiary. Congress added it to approximate the second-level (shareholder) tax that would apply if the US business were run through a US corporation paying dividends to its foreign parent.

The mechanics are a second tax stacked on top of the section 882 net-basis tax. The branch profits tax is imposed on the corporation's dividend-equivalent amount, which equals the year's effectively connected earnings and profits, reduced by any increase in US net equity and increased by any decrease in US net equity. US net equity is, broadly, the branch's US assets minus its US liabilities — so reinvesting earnings into the US business (raising net equity) shrinks the dividend-equivalent amount, while pulling equity out (lowering it) enlarges it. Treasury Regulation 1.884-1 sets the rate at 30% of the dividend-equivalent amount, in addition to the section 882 tax. On the return this is the Section III computation.

A treaty can reduce or eliminate the branch profits tax, but only on section 884's terms: under section 884(e), a treaty helps only if it is an income tax treaty and the foreign corporation is a qualified resident of the treaty country. Where the treaty has no specific branch-profits article, the Code generally looks to the treaty's dividend rate for a wholly owned subsidiary paying its corporate parent. The form reflects this by applying 30% or a lower treaty rate if the corporation is a qualified resident or otherwise qualifies for treaty benefits.

A foreign corporation that concludes it owes no US tax — because a treaty exempts the income, or because its US activity does not rise to a US trade or business — still usually files a protective Form 1120-F. The reason is in Treasury Regulation 1.882-4: a foreign corporation gets deductions and credits against ECI only if it files a true and accurate return, and the regulation provides a specific protective-return mechanism to preserve that right if the no-tax determination later proves wrong.

The downside of skipping it is severe. The 1120-F instructions state in plain terms that a corporation that does not file a return can lose the right to take deductions and credits against effectively connected income — turning what should have been a net-basis tax into something closer to a tax on gross receipts if the IRS later finds ECI. A protective return is, in effect, a low-cost option premium that keeps the deduction door open.

This is also why "no permanent establishment" is not the same as "no filing." The instructions specifically direct a corporation that initially determines it has no US tax under a treaty — for example because its income is not attributable to a US permanent establishment — to file a protective return and attach Form 8833 where required. We treat the full protective-filing mechanics, deadlines, and the 18-month rule in a dedicated guide rather than repeating them here.

Treaty analysis starts with section 894 and moves to the relevant treaty's business profits and permanent establishment articles — commonly Article 7 and Article 5. The Form 1120-F asks the questions directly: whether the corporation had a permanent establishment in the United States under a treaty, and whether it is taking a position that a treaty overrides the Code to reduce its tax — in which case Form 8833 is generally required under section 6114.

Recent case law shows how fact-driven these calls are. In YA Global Investments, LP, the Tax Court held the partnership was engaged in a US trade or business and rejected the argument that its US manager was an independent agent — emphasizing the manager's agency status, the retained control, and the manager's negotiation of hundreds of contracts, with the income then attributed through the US office. That case is a warning for foreign funds and corporations that use US managers, advisers, or affiliates to originate or negotiate deals: a dependent agent can create a US trade or business (and, by extension, a permanent establishment) even without a traditional office.

On the procedural side, the live authorities on late-filed returns are Swallows Holding, Ltd. v. Commissioner and Adams Challenge (UK) Ltd. v. Commissioner. The IRS continues to teach examiners that these cases are central to the loss of deductions and credits when a foreign corporation files its 1120-F late — Swallows upholding the regulatory timing standard for claiming deductions, and Adams Challenge reinforcing the consequences of delinquency. Together they are the reason protective filing is treated as a best practice rather than an afterthought.

The structural choice is not merely administrative — it changes the core taxing regime and, critically, the second-level tax. Three common structures sit on a spectrum:

Disregarded US LLC owned by a foreign person. Income-tax-transparent to the owner; at the entity level it triggers the section 6038A information-reporting regime (Form 5472 + pro forma 1120). The owner's own US tax then depends on what the activity is and who owns the LLC — and, if the owner is itself a foreign corporation, can pull in a 1120-F (section 4).

Foreign corporation operating directly as a US branch. Moves the analysis into Form 1120-F, sections 881/882, treaty disclosure, and — the headline cost — the section 884 branch profits tax plus branch-level interest rules. It can simplify legal ownership, but it introduces that second layer on repatriated branch earnings.

US C-corporation owned by the foreign parent. Stays in the regular Form 1120 world (related-party transactions can still trigger Form 5472). Here the second-level tax is not branch profits tax but the more familiar dividend withholding when profits are actually distributed to the foreign parent — frequently reduced by treaty.

The decision in one line: for a passive or genuinely no-US-trade-or-business owner, the disregarded-LLC information-report path is usually the lighter touch (file 5472, watch the USTB line). Once there is a real US business, the choice becomes direct foreign-corp branch (1120-F + branch profits tax) versus US C-corp (1120 + dividend withholding) — and the right answer turns on modeling that second-level tax, the treaty's branch-profits and dividend rates, and the corporation's qualified-resident status, not on filing convenience. Because the stakes are entity-level and treaty-specific, model the economics before converting.