Introduction
Quick answer: Form 1120 is the US corporate income tax return used to report income, deductions, and tax liability. Form 5472 is a separate information return used to disclose transactions between a US entity and its foreign owner or related parties. For a foreign-owned single-member LLC, only Form 5472 applies — but it must be submitted attached to a "pro forma" Form 1120, a stripped-down cover document that has no tax function of its own. Missing this package can trigger a $25,000 penalty per form.
If you've been trying to figure out which tax forms your foreign-owned US LLC needs to file, you've probably come across both Form 5472 and Form 1120. The two are connected — but they serve completely different purposes, and confusing one for the other leads to some of the most common filing mistakes non-US founders make.
This guide breaks down exactly what each form does, why a foreign-owned disregarded entity files one but not the other (and why the pro forma version of that other one still shows up anyway), and what the key differences mean in practice.
What is Form 1120?
Form 1120 is the standard US Corporation Income Tax Return. According to the IRS, domestic corporations use it to report income, gains, losses, deductions, and credits, and to calculate their income tax liability for the year.
Form 1120 is, at its core, a tax return. It determines what a corporation owes. It covers:
- Gross income and total deductions
- Taxable income and tax due
- Tax credits and estimated tax payments
- Signed declarations from an officer of the corporation
C-corporations file Form 1120 every year, regardless of whether they had income. It's a substantive return with real tax consequences.
What is Form 5472?
Form 5472 — formally titled "Information Return of a 25% Foreign-Owned U.S. Corporation or a Foreign Corporation Engaged in a U.S. Trade or Business" — is not a tax return. It doesn't calculate or assess any tax. Instead, it's a disclosure document.
Its purpose is to give the IRS visibility into transactions between a US entity and its foreign owner or related parties. These are called "reportable transactions," and they include contributions, distributions, loans, property transfers, fees paid personally on the LLC's behalf, and similar exchanges. The IRS uses this information to monitor cross-border financial activity, not to compute tax liability.
The key distinction: Form 1120 determines tax owed. Form 5472 reports who is involved and what moved between them.
Why does Form 5472 need a pro forma Form 1120?
This is where foreign-owned single-member LLCs run into something that doesn't immediately make sense: they're told to file a Form 1120 alongside their Form 5472, even though they're a disregarded entity that doesn't file a corporate tax return.
Here's why. A single-member LLC is a disregarded entity for US income tax purposes — the IRS doesn't treat it as separate from its owner for income reporting. That means no standalone Form 1120. But IRS regulations under Section 6038A treat foreign-owned disregarded entities as corporations solely for the purpose of the Form 5472 reporting requirement.
Since Form 5472 can't be submitted to the IRS on its own, it needs to be attached to something. For a corporation, that something is the regular Form 1120. For a foreign-owned disregarded entity — which has no real Form 1120 to attach to — the IRS requires a pro forma Form 1120: a simplified version of the corporate return that exists only as a filing vehicle.
The pro forma Form 1120 has no tax function. No income tax is computed. No tax is owed through it. It carries the LLC's basic identification information and serves as the envelope that gets Form 5472 to the IRS.
What does a foreign-owned single-member LLC actually file?
A foreign-owned single-member LLC does not file a standard Form 1120. It is not a corporation, and it owes no corporate income tax through this filing process.
What it does file — when it has reportable transactions with its foreign owner — is:
- Form 5472, disclosing the transactions that occurred during the tax year
- A pro forma Form 1120, completed with the LLC's basic information and used only to submit Form 5472
These two documents are filed together as a single package, generally due by April 15 following the close of the tax year. The pro forma Form 1120 carries no tax consequence of its own. Its sole function is to accompany Form 5472 to the IRS.
The most common misconceptions about these two forms
"My LLC is a disregarded entity, so I don't file anything."
Disregarded entity status eliminates the need for a standard Form 1120, but it doesn't eliminate the Form 5472 requirement. IRS regulations specifically created the pro forma Form 1120 process to handle this gap.
"Form 5472 is just part of Form 1120."
They're two separate documents with two separate purposes. Form 5472 is the required information return. The pro forma Form 1120 is the submission wrapper. Neither substitutes for the other.
"No income means no filing."
Form 5472 is triggered by reportable transactions, not by taxable income. An LLC that never earned a dollar can still owe a Form 5472 filing if money moved between the owner and the LLC — even something as routine as a capital contribution or a formation cost paid personally.
"The pro forma Form 1120 means I owe corporate tax."
No. The pro forma Form 1120 filed by a foreign-owned disregarded entity does not generate corporate income tax. It exists purely to transmit Form 5472 to the IRS.
What happens if you file Form 1120 instead of a pro forma Form 1120?
Filing a full standard Form 1120 when a pro forma is what's required — or filing Form 5472 without any Form 1120 attached — creates a materially incomplete or incorrect filing. The IRS has specific requirements for how foreign-owned disregarded entities must submit these forms.
An incorrect or incomplete filing carries the same $25,000 penalty exposure as a missing one. Getting the structure right, a pro forma Form 1120 with Form 5472 attached, filed as a single package, is as important as filing on time.
Comparing Form 5472 and Form 1120 side by side
| Form 5472 | Pro forma Form 1120 | |
|---|---|---|
| Purpose | Report related-party transactions | Cover return that carries Form 5472 |
| Type | Information return | Income tax return form, used pro forma here |
| Computes tax? | No | Not for a disregarded entity filing pro forma |
| Signature / preparer info | Not the document that carries it | Contains the applicable signature and paid preparer information |
| Filed alone? | No — attached to the pro forma return | Submitted together with Form 5472 |
What does a foreign-owned single-member LLC actually file?
A foreign-owned single-member LLC does not file a standard Form 1120. It is not a corporation, and it owes no corporate income tax through this filing process.
What it does file — when it has reportable transactions with its foreign owner — is:
- Form 5472, disclosing the transactions that occurred during the tax year
- A pro forma Form 1120, completed with the LLC's basic information and used only to submit Form 5472
These two documents are filed together as a single package, generally due by April 15 following the close of the tax year. The pro forma Form 1120 carries no tax consequence of its own. Its sole function is to accompany Form 5472 to the IRS.
The most common misconceptions about these two forms
"My LLC is a disregarded entity, so I don't file anything."
Disregarded entity status eliminates the need for a standard Form 1120, but it doesn't eliminate the Form 5472 requirement. IRS regulations specifically created the pro forma Form 1120 process to handle this gap.
"Form 5472 is just part of Form 1120."
They're two separate documents with two separate purposes. Form 5472 is the required information return. The pro forma Form 1120 is the submission wrapper. Neither substitutes for the other.
"No income means no filing."
Form 5472 is triggered by reportable transactions, not by taxable income. An LLC that never earned a dollar can still owe a Form 5472 filing if money moved between the owner and the LLC — even something as routine as a capital contribution or a formation cost paid personally.
"The pro forma Form 1120 means I owe corporate tax."
No. The pro forma Form 1120 filed by a foreign-owned disregarded entity does not generate corporate income tax. It exists purely to transmit Form 5472 to the IRS.
What happens if you file Form 1120 instead of a pro forma Form 1120?
Filing a full standard Form 1120 when a pro forma is what's required — or filing Form 5472 without any Form 1120 attached — creates a materially incomplete or incorrect filing. The IRS has specific requirements for how foreign-owned disregarded entities must submit these forms.
An incorrect or incomplete filing carries the same $25,000 penalty exposure as a missing one. Getting the structure right, a pro forma Form 1120 with Form 5472 attached, filed as a single package, is as important as filing on time.
Frequently asked questions
Sources
- IRS — Instructions for Form 5472
- IRS — Instructions for Form 1120
- IRS — Single member limited liability companies
Rules can change and many situations have exceptions. Where guidance is nuanced, the IRS instructions above control.
