If you’re a non‑U.S. founder running a U.S. company, you’ve probably heard form numbers thrown around like alphabet soup—1120, 1065, 5472, 5471, 1040‑NR, 1040. Knowing which forms apply to your situation, when they’re due, and what they actually report is the difference between smooth sailing and expensive penalties.
This deep guide explains each major U.S. tax form foreign‑owned startups encounter, how to tell which ones are yours, and what to do to stay compliant.
Who this guide is for
You’ll find this useful if you’re a foreign owner of a U.S. LLC or corporation, a founder with partners abroad, or a U.S. company planning foreign subsidiaries. The language is simple and direct, so you can understand the essentials even if English isn’t your first language.
Where needed, we’ll point out deadlines, penalties, and the role Bookmate plays in getting these filed correctly.
The quick matching logic (start here)
Let’s keep it very simple. Not every form applies to every company. The form you file depends on the type of U.S. business you have and how it’s owned. If you don’t have a U.S. company, these forms don’t apply. If you do, here’s the easy breakdown:
- If you set up a C‑Corporation (the standard Delaware startup company), you file Form 1120 every year.
- If you set up an LLC with two or more owners and you didn’t choose to be taxed as a corporation, you file Form 1065 (partnership return) and give each owner a K‑1.
- If you set up a single‑member LLC and you are a foreign owner, you usually file Form 5472 together with a short “cover page” called a pro forma Form 1120—especially if you moved money in or out of the company.
- If your U.S. company owns another company abroad, then you may need to attach Form 5471 to your corporate return.
- On the personal side: if you are a non‑U.S. person with U.S. income (like through a partnership), you may need Form 1040‑NR. If you move to the U.S. and become a resident for tax purposes, you switch to Form 1040.
Think of it like this: your company type decides the main return (1120, 1065, or pro forma 1120 + 5472). Special situations like owning foreign subsidiaries add more forms (5471). Your personal situation decides whether you also file 1040‑NR or 1040.
Form 1120 — U.S. Corporation Income Tax Return
Who files: U.S. corporations, including Delaware C‑Corporations widely used for venture‑backed startups. Foreign‑owned C‑Corps file the same Form 1120 as U.S.‑owned ones.
What it reports: Income, deductions, credits, and tax for the corporation. It also serves as the cover for many corporate‑level schedules (for example, Schedule G for information on certain owners, and other statements about activities or credits claimed).
If the U.S. corporation owns foreign subsidiaries, Form 1120 is sometimes accompanied by separate international information returns, including Form 5471 (explained later).
When it’s due: For calendar‑year corporations, the original due date is generally April 15. If you file an extension with Form 7004, the filing due date is typically October 15. An extension gives more time to file, not to pay. If tax is due, interest and penalties can accrue after April 15.
Common founder mistakes: Waiting until the last minute; not reconciling books to the return; treating shareholder transfers as non‑events (some are loans or paid‑in capital and must be recorded correctly). Another frequent error is assuming that having no revenue means there is nothing to file—corporations must still file Form 1120 annually once formed.
Founder example: A Singapore‑based founder forms a Delaware C‑Corp to raise U.S. venture capital. Even in a pre‑revenue year, the company files Form 1120 to report expenses and maintain compliance. If the company later creates a subsidiary in Europe, international schedules may be required alongside the 1120.
Pro forma Form 1120 with Form 5472 — for foreign‑owned single‑member LLCs
Who files: A U.S. single‑member LLC that is at least 25% foreign‑owned and treated as disregarded for U.S. tax purposes must file Form 5472 for reportable transactions with its foreign owner or related parties.
Because Form 5472 cannot be filed alone, the LLC submits a pro forma Form 1120 (a short, mostly blank 1120 used as a cover sheet) and attaches the completed Form 5472.
What it reports: Form 5472 discloses related‑party transactions between the LLC and foreign owners or related entities. These include capital contributions, loans, interest, rent, royalties, management fees, cost sharing, reimbursements, and many other transfers—even if the company has no revenue yet.
The IRS uses this to monitor cross‑border flows and transfer pricing risk.
When it’s due: Same calendar as corporate returns: April 15 for calendar‑year entities, with an October 15 extended deadline if Form 7004 is filed on time.
Penalties: The IRS can assess $25,000 per missed or incomplete Form 5472, with additional $25,000 increments if the failure continues after notice. This penalty applies even in zero‑revenue years if there were reportable related‑party transactions.
Common founder mistakes: Assuming “no sales” means “no filing”; forgetting that simple owner funding or reimbursements can be reportable; trying to file Form 5472 without the pro forma 1120; poor documentation of intercompany activity.
Founder example: A Canadian founder forms a single‑member Delaware LLC to build a SaaS app. During the first year, the owner wires $40,000 from a foreign personal account to pay U.S. contractors.
Even with no revenue, those transfers are reportable transactions, so the LLC must file Form 5472 attached to a pro forma 1120 by April 15 (or October 15 with extension).
Form 1065 — U.S. Return of Partnership Income (multi‑member LLCs)
Who files: A multi‑member LLC that did not elect corporate taxation is a partnership for U.S. tax purposes. It files Form 1065 to report the partnership’s income and expenses.
The partnership does not itself pay income tax; instead, it issues Schedule K‑1 to each partner showing that partner’s share. For international situations, Schedule K‑2/K‑3 may apply to report foreign‑related items.
What it reports: A full picture of the LLC’s operations for the year and each partner’s share. If there are foreign activities, credits, withholding, or other international tax items, K‑2/K‑3 extend the disclosure. Partners then use their K‑1 (and sometimes K‑3) to file their own returns in the U.S. or abroad.
When it’s due: For calendar‑year partnerships, the original deadline is March 15 (in 2025, it’s March 17 because the 15th falls on a Saturday). With a timely Form 7004 extension, the final deadline is September 15.
Penalties: The IRS imposes a monthly penalty for late filing—currently $240 per partner, per month, up to 12 months—plus separate penalties for late or missing K‑1s. Extensions extend the time to file, not to furnish K‑1s late without penalty.
ITIN note for foreign partners: A partnership can issue a K‑1 to a foreign partner even if that partner does not yet have an ITIN. However, if a foreign partner must personally file a U.S. Form 1040‑NR, they will need an ITIN for that filing.
Founder example: Two founders in Spain and Brazil own a Wyoming LLC taxed as a partnership. The LLC files Form 1065 by March 17, delivers K‑1s to both partners, and completes K‑2/K‑3 because some customers and income are outside the U.S. If either founder has a U.S. filing requirement, they file 1040‑NR and obtain an ITIN.
Form 1040‑NR — U.S. Nonresident Alien Income Tax Return (individuals)
Who files: A non‑U.S. individual with U.S.‑source income that is effectively connected with a U.S. trade or business (or certain other U.S.‑source income) may need to file Form 1040‑NR. Many foreign founders never need this form; others absolutely do. The trigger is your personal U.S. tax exposure, not merely owning a U.S. company.
What it reports: U.S.‑source income taxable to a nonresident, deductions connected to that income, and any treaty positions claimed. Common examples include consultant fees for work performed in the U.S., partnership income that is effectively connected to a U.S. trade or business, or wages if a founder briefly worked in the U.S.
If you are only a shareholder in a C‑Corp and did not have U.S.‑source personal income, 1040‑NR may not be required.
When it’s due: The due date depends on the type of income. Typically it’s April 15 if you had wages subject to withholding. In other cases, a nonresident without wages may have until June 15. A personal extension is available with Form 4868, often pushing the deadline to October 15.
Deadlines can vary with facts, so it’s smart to check your exact situation.
ITIN requirement: To file 1040‑NR you usually need an ITIN. Bookmate does not process ITIN applications, but we partner with theitin.com for this purpose: theitin.com.
Founder example: A Nigerian founder owns a minority interest in a U.S. partnership that allocates effectively connected income to her. She files 1040‑NR and claims any treaty benefits available. If she has no personal U.S.‑source income in a future year, she may not need to file 1040‑NR for that year.
Form 1040 — U.S. Individual Income Tax Return (resident individuals)
Who files: If a founder becomes a U.S. tax resident under the green card or substantial presence tests, they generally file Form 1040 as a resident for the period of residency. Some founders have a dual‑status year when they move to the U.S.; these returns are more complex.
What it reports: Worldwide income for the period of U.S. residency, with credits or exclusions that may apply under treaty or domestic rules. This is different from 1040‑NR, which focuses on U.S.‑source income for nonresidents.
When it’s due: Usually April 15, with a personal extension to October 15 via Form 4868.
Founder example: A founder from the U.K. moves to New York in September to build the company from the U.S. For that year, they may have a dual‑status return: nonresident part of the year (no 1040 reporting on early foreign income) and resident for the remainder (1040 reports worldwide income during the resident portion). Planning ahead avoids surprises.
Form 5471 — Information Return of U.S. Persons With Respect to Certain Foreign Corporations
Who files: U.S. persons (including U.S. corporations and sometimes individuals) who are officers, directors, or certain shareholders of foreign corporations must file Form 5471 in several common situations.
For startup founders, the most frequent case is a U.S. corporation that owns shares in a foreign subsidiary. Ownership percentages and changes in control determine which category of filer you are and which schedules you must complete.
What it reports: Detailed information about the foreign corporation’s ownership, income, assets, and transactions with related parties. The form is extensive; getting it right requires good books and clear intercompany documentation.
When it’s due: Form 5471 is filed as an attachment to the filer’s main return. For a U.S. corporation, that means it is due with the Form 1120 deadline (April 15 for calendar‑year, October 15 if extended). If an individual must file 5471 (for example, a U.S. individual who directly owns a foreign corporation), it is due with that person’s Form 1040.
Penalties: Missing, incomplete, or late 5471s can trigger $10,000 penalties per form, per year, with additional penalties and statute‑of‑limitations issues if not corrected after notice.
Founder example: Your Delaware C‑Corp acquires a 60% stake in a Kenyan operating company. Because the U.S. corporation now owns a foreign corporation, you likely have a Form 5471 filing attached to the 1120. The exact schedules depend on the filer category.
How these forms interact in real life
A single startup can touch several forms over its life. In year one, a foreign‑owned single‑member LLC may only need pro forma 1120 + 5472 because of owner funding. In year two, after adding a cofounder, the entity may become a partnership and switch to Form 1065 with K‑1s and K‑2/K‑3.
Later, after raising a seed round and converting to a Delaware C‑Corp, the company starts filing Form 1120. If it expands overseas and opens a foreign subsidiary, Form 5471 joins the package. Meanwhile, founders themselves may or may not have personal U.S. filings like 1040‑NR; that depends on their personal U.S.‑source income and tax residence.
The main idea: filings change as your structure and activities change. Keeping clean books and documenting cross‑border activity makes these transitions much easier.
Deadlines at a glance (and what happens if you’re late)
- Form 1120: April 15 (Oct 15 with extension). Late filing can trigger failure‑to‑file and failure‑to‑pay penalties and interest.
- Pro forma 1120 + 5472: April 15 (Oct 15 with extension). Missing or incomplete 5472 can cost $25,000 per year, per form.
- Form 1065: March 15 (March 17 in 2025); Sept 15 if extended. Late filing penalty generally $240 per partner per month, up to 12 months, plus penalties for late K‑1s.
- Form 1040‑NR / 1040: Usually April 15; certain nonresidents without wages may have until June 15; Oct 15 with extension.
- Form 5471: Due when the main return is due (1120 or 1040). Penalties start at $10,000 per form for late or incomplete filings.
If you discover a miss, act fast. Many penalties escalate the longer you wait, but accurate catch‑up filings can often stop the clock.
What Bookmate does (and does not do)
Bookmate focuses on federal U.S. tax filings for startups owned by non‑U.S. founders. We prepare and file 1120, 1065 (with K‑1s and K‑2/K‑3), pro forma 1120 + 5472, and 5471 attached to corporate returns.
If you personally need to file 1040‑NR because of U.S.‑source income, we can include it in your overall compliance plan. We do not apply for ITINs or EINs on your behalf. For ITINs, we partner with theitin.com: theitin.com.
For EINs, we do not handle the application directly, but we can recommend trusted formation companies who assist with this process.
State‑level items (Delaware franchise tax, Wyoming annual report) are handled by your registered agent or formation company, not by Bookmate. We coordinate timing so your state and federal obligations stay aligned.
Final checklist before tax season
Confirm your entity type and ownership; review the list above and note the forms that match your situation. Make sure your bookkeeping is current and that intercompany or owner transfers are clearly labeled (capital contribution, repayable loan, reimbursement, services).
Decide whether you need to extend—extensions protect you from late‑filing penalties while you finish accurate returns, but they don’t postpone tax payments. Keep copies of all filings and confirmations.
Talk to Bookmate
Every founder’s tax situation is unique, and the forms you file will change as your company grows. Book a call and we’ll map your structure to the correct filings, prepare what the IRS expects, and keep you penalty‑free.
Learn more at trybookmate.co or book a consultation here: book a consultation.
With the right partner and a clear plan, U.S. tax compliance becomes simple and predictable—so you can stay focused on building the business you set out to create.
