Pro Forma 1120: The Required Attachment to Form 5472 (2026)

Form 1120 is normally the US Corporation Income Tax Return — the form a C-corporation uses to report its income and pay its 21% federal tax. A pro forma 1120 is something different: it is the same physical form, but used as an empty shell. The Latin pro formameans “as a matter of form” — the document is filed to satisfy a formality, not to report a real tax position.

A foreign-owned disregarded entity does not owe corporate income tax (it is disregarded), so it has no figures to put on the 1120. But it cannot file Form 5472 by itself. The IRS regulations require Form 5472 to be attached to an income tax return, and the only return a disregarded entity can use is the 1120. The solution is the pro forma 1120: a blank 1120 that does nothing but hold Form 5472 and give the IRS an envelope to log.

Why it confuses people

Founders see “Form 1120 — Corporation Income Tax Return” and panic, assuming they now owe corporate tax or must compute corporate income. They do not. The pro forma 1120 has no tax consequences. It is a wrapper. Understanding this removes most of the fear around the foreign-owned LLC filing.

The requirement flows directly from how the 2017 regulations were written. Final regulations under Treasury Decision 9796 treat a foreign-owned disregarded entity as a corporation for the reporting rules of IRC section 6038A. Section 6038A ties Form 5472 to the filing of a corporate income tax return. So when the regulations made the LLC a “reporting corporation,” they also pulled in the requirement to file a 1120 — even though the LLC owes no corporate tax.

The IRS resolved the contradiction by directing foreign-owned disregarded entities to file a pro forma 1120: complete only the identifying information, attach Form 5472, and submit the two together. The pro forma 1120 is therefore not optional and not a separate choice — it is the vehicle that makes the Form 5472 filing valid.

Filling out a pro forma 1120 is mostly about knowing what to leave blank. The form has dozens of lines; for a disregarded entity, almost all of them stay empty.

The step-by-step walkthrough of every line is covered in the companion pro forma 1120 instructions. The short version: identification block in, everything else out, Form 5472 attached, “Foreign-owned U.S. DE” across the top.

This is the most reassuring fact about the whole filing: there is no tax to pay with a pro forma 1120. The entity is disregarded for income tax, so the income lines are blank and the tax lines are blank. You are not computing 21% corporate tax. You are not sending a check. The pro forma 1120 is a disclosure document, not a payment document.

That said, a non-resident owner may have separate US tax obligations on US-source income — for example, if the LLC's activity rises to a US trade or business, the owner might need to file a Form 1040-NR. But that is the owner's personal return, entirely distinct from the entity's pro forma 1120. The pro forma 1120 itself never carries tax.

The pro forma 1120 plus Form 5472 follows the special filing rules for foreign-owned disregarded entities, and those rules allow only mail or fax. Tax software that e-files a normal 1120 will not transmit this pro forma package. There is no exception and no online portal for it.

Keep dated proof of filing. Because the $25,000 penalty turns on whether you filed on time, a certified-mail green card or a fax confirmation page is your evidence if the IRS ever questions the filing date.

The pro forma 1120 shares Form 5472's deadline because they are filed as one package. For a calendar-year entity that means April 15 following the tax year. A six-month extension to October 15 is available by filing Form 7004 on or before April 15.

Because the pro forma 1120 carries no tax, the extension only moves the filing deadline — there is nothing else to extend. File Form 7004 by April 15 to claim the extra time.

The penalty is not a “pro forma 1120 penalty” — it is the Form 5472 penalty, and it is severe: $25,000 per form, per year, with no maximum and no statute of limitations, plus $25,000 for each 30-day period after a 90-day IRS notice. But the pro forma 1120 matters because it is part of a complete filing.

If you mail Form 5472 without the pro forma 1120 wrapper, the IRS can treat the filing as substantially incomplete — which, under section 6038A, is the same as not filing at all. So the pro forma 1120 is not a technicality; omitting it can cost the full $25,000. The two must always travel together.

For a flat $299, form5472.tax completes the pro forma 1120 correctly, prepares Form 5472, has a specialist review the package, and files it the right way — saving $248 versus form5472.online. The companion guides on the pro forma 1120 instructions and filing both together walk through the full process.