Form 1120: the corporation return
This page is general information, not tax advice for your situation.
Form 1120 is the US Corporation Income Tax Return. It is the return a corporation files, and it is the return an LLC files when it has elected to be taxed as a corporation. It computes tax. That last point is the one that causes the most confusion, because the same number, 1120, also appears on the cover sheet that carries a Form 5472. This page explains who files the real Form 1120, what it is, and how it differs from the pro forma 1120.
Who files Form 1120
A corporation files Form 1120. So does an LLC that elected corporate treatment with Form 8832, the form that makes an association taxable as a corporation. The election changes how the LLC is taxed: instead of being disregarded or taxed as a partnership, the LLC is taxed as a corporation, and the corporation return follows.
The election is a choice with consequences that reach beyond the return. A corporation is taxed on its income, and distributions to owners are taxed again as dividends. That is the structure of corporate taxation, and it is the reason the election is made deliberately, not by accident. This page covers the return, not the choice itself. If the election is already made, the return is Form 1120.
What the return is
Form 1120 is the US Corporation Income Tax Return. It reports the corporation's income, deductions and credits, and it computes the tax owed. It is a full tax return, not an information return and not a cover sheet. The figures on it decide the tax, and the tax is due with the return, subject to the extension rules below.
That is the sharpest difference from Form 5472. Form 5472 is an information return: it reports transactions between the LLC and its foreign owner or a related party, and no tax is computed on it. Form 1120 computes tax. The two forms serve different purposes, and an LLC can owe one, the other, or, in some cases, both, depending on its classification and its transactions. A tax professional should confirm which forms a particular LLC owes.
Pro forma 1120 versus the real 1120
The pro forma Form 1120 is a cover sheet for Form 5472, and nothing more. Write "Foreign-owned U.S. DE" across the top, fill in the name and address, item B (the EIN) and item E, and leave the rest blank. No tax is computed on it, and no tax is due with it. It exists so that the Form 5472 has a return to attach to.
The real Form 1120 is filled in in full. It carries income, deductions, credits and the tax computation. The two forms share a number and little else, and confusing them is the most common mistake on this page. Filing a pro forma 1120 when a real 1120 is owed leaves the corporation return unfiled, and the unfiled return carries its own consequences. Filing a real 1120 when only a pro forma is needed creates a tax computation where none belongs.
The test is the classification. A foreign-owned single-member LLC that is a disregarded entity files Form 5472 with a pro forma 1120. An LLC that elected corporate treatment files the real Form 1120. If you are unsure which one your LLC is, check the election before you file, not after.
Due date and extension
Form 1120 is due April 15 for a calendar-year corporation, the 15th day of the 4th month after the end of the tax year. Tax year 2026 is due April 15, 2027, a Thursday. Form 7004 filed by April 15 extends the filing date by six months, to October 15, 2027.
An extension extends the filing date, not the payment date. The tax computed on Form 1120 is due on the original date, and interest can run on a late payment even when the return itself is filed on time under an extension. That is different from Form 5472, where there is usually no tax to pay and the extension covers the filing in full. If the corporation expects to owe tax, the payment should be made by April 15 whether or not the return is extended.
Common mistakes
The first mistake is filing a pro forma 1120 when a real 1120 is owed. The second is the reverse: filing a full Form 1120 for a disregarded entity that only owes a Form 5472 with a pro forma cover sheet. The third is missing the April 15 date, on the assumption that a corporation return follows a different calendar. It does not: April 15 is the date for a calendar-year corporation, the same date as Form 5472.
The fourth mistake is treating the extension as an extension of the payment date. It is not. The fifth is assuming that the Form 5472 duty disappears when corporate treatment is elected. Whether a Form 5472 is also owed depends on the facts of the LLC and its transactions, and a tax professional should confirm it. Do not assume the election settles the question.
What to do next
Confirm the classification first: is the LLC a disregarded entity, a partnership, or a corporation by election? Then check the deadline: April 15, 2027 for tax year 2026, with an extension to October 15 on Form 7004. Then write to us about the return you need. The order flow is coming. Form 1120 costs $249 regular or $299 express; an extension on Form 7004 is $19.
A late corporation return costs 5% of the unpaid tax per month, up to 25%.
Federal Returns handles five individual filings: Form 5472, Form 1065, Form 1120, Form 1040-NR and the FBAR (FinCEN Form 114, a FinCEN report, not a tax return). Flat prices from $99, regular or express, and the order flow is coming. Write to us about the filing you need.
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