US tax forms explained
What 1120, 1120-S, 5472, and 1040-NR are, and which one applies to your entity — in plain language.
US tax forms are an alphabet soup, and the wrong one is a common and expensive mistake for non-resident founders. Here's what each of the forms in a FormBridge US tax packet is and who it's for. Which ones apply to you depends on your entity type, your ownership, and your residency — the Tax autopilot works that out from your company records.
- Form 1120
- The US Corporation Income Tax Return. This is the annual federal return a C-Corporation files to report its income, deductions, and tax. If you formed a Delaware C-Corp, this is your main return.
- Form 1120-S
- The income tax return for an S-Corporation — a corporation that has elected pass-through taxation. It reports income that flows through to the owners' personal returns rather than being taxed at the entity level.
- Form 5472
- An information return for a US company with a foreign owner (including a foreign-owned single-member LLC). It reports transactions between the company and its foreign owner. It carries steep penalties for non-filing, which makes it one of the most important forms for non-resident founders.
- Form 1040-NR
- The US Nonresident Alien Income Tax Return — the personal return a non-resident individual files when they have US-source income that is taxable to them personally.
Which form applies
| Your situation | Forms typically involved |
|---|---|
| Delaware C-Corp | 1120 (corporate return); 5472 if there is a foreign owner |
| Foreign-owned single-member LLC | 5472 with a pro-forma 1120 |
| Corporation with an S-election | 1120-S (pass-through corporate return) |
| Non-resident with US-source personal income | 1040-NR |
A foreign-owned single-member US LLC is often treated as "disregarded" for income tax, which leads many founders to assume they have nothing to file. They still owe a Form 5472, and missing it carries a significant penalty. The Compliance and Tax autopilots track this obligation so it doesn't slip — see staying compliant.
This is general information about what these forms are, not tax advice and not a determination of what you must file. A licensed CPA partner confirms the right forms for your situation before anything is signed — see the CPA handoff.
Filing outside the US? See UK Corporation Tax. Choosing an entity for the first time? Start with choosing your entity and jurisdiction.