The single-member US LLC has become the default vehicle for international founders selling into the US market: formed online in a day, no US corporate tax if the owner stays offshore with no US operations, accepted by Stripe and US banks. All of that is broadly true. What the formation websites tend to leave out is the filing that keeps it true — and the US$25,000 penalty waiting behind it.

The rule in one paragraph

Since 2017, a US LLC that is wholly owned by one foreign person (individual or company) and disregarded for tax purposes is treated as a US corporation for reporting purposes only. Each year it has “reportable transactions” with its owner or other related parties, it must file Form 5472, stapled to a pro forma Form 1120, and maintain records supporting the figures. “Reportable transactions” is read broadly — it includes the money you put into your own LLC (capital contributions), money you take out, loans either way, and payments between the LLC and any related company.

In other words: for almost any foreign-owned single-member LLC that is actually used, the filing is required every year — profit or loss, activity or near-dormancy, US tax due or not.

What it is not

Form 5472 is an information return, not a tax return. Filing it does not by itself make the owner taxable in the US; a non-resident whose LLC has no US “trade or business” and no US-source income can file 5472 annually and owe nothing. Conversely, not filing it does not make tax appear — it just makes penalties appear:

  • US$25,000 per missed or substantially incomplete form, per year;
  • Another US$25,000 per 30-day period if not cured after IRS notice;
  • No ceiling on the escalation, and the statute of limitations stays open.

The penalty is automatic in administration: notices are computer-generated when a known filer goes silent. For a two-person startup, a US$25,000 letter over a form nobody mentioned is an existential event.

Common situations that trigger it

  • A Hong Kong or Singapore founder running a SaaS or e-commerce business through a Wyoming or Delaware LLC;
  • A Canadian investor holding a US rental property in a single-member LLC (with the separate caution that Canada’s tax treatment of US LLCs is unfavourable — Canadians should rarely use LLCs at all without advice);
  • A foreign parent company with a disregarded US subsidiary;
  • A dormant LLC that received even one capital contribution during the year — that contribution alone is a reportable transaction.

Multi-member LLCs are different (they file partnership returns — Form 1065, with their own foreign-partner reporting), and foreign corporations doing US business file Form 1120-F. The 5472-plus-pro-forma-1120 regime is specifically the single foreign owner pattern.

The housekeeping that comes with it

To file at all, the LLC needs an EIN (obtainable for foreign owners without an SSN, by a process worth doing correctly the first time). The form requires identifying the owner and any related parties, and quantifying the year’s transactions with each — which presumes books that separate the LLC’s money from the owner’s. The casual habit of treating an LLC account as a personal wallet is what turns this simple filing into an expensive reconstruction.

Deadlines follow the corporate calendar: April 15 for calendar-year filers, extendable to October 15 — but the extension must be requested by the original deadline. Note also that the form cannot be e-filed in this pro forma configuration; it goes by mail or fax to a dedicated IRS unit, which is its own small ritual.

And the bigger question behind it

Form 5472 compliance is necessary but not sufficient. The questions that actually determine a foreign founder’s US tax bill — does the LLC have a US trade or business? is there effectively connected income? does a treaty (Canada’s, say — not Hong Kong’s, as there is none) shield it? should the structure be an LLC at all, or a C corporation? — deserve an answer before the business scales. The LLC’s famous tax-transparency is a feature only when the facts genuinely keep the owner outside the US tax net; when they do not, the same structure quietly generates unfiled US obligations year after year.

If you already own a US LLC and the words “Form 5472” are new to you, the situation is usually fixable — penalty exposure depends heavily on how the catch-up is handled, and reasonable-cause relief is realistic for owners who acted promptly once informed. The key word is promptly.