PFIC Tax Rules for US Investors Abroad: UK Funds, ISAs & ETFs

Most non-US pooled investments — UK OEICs, unit trusts, investment trusts, ETFs, and the funds inside a stocks-and-shares ISA — are treated by the IRS as Passive Foreign Investment Companies (PFICs). Under the PFIC tax rules for US investors abroad, gains and distributions can be taxed at the highest ordinary rates plus an interest charge, and each holding is reported annually on Form 8621. An ISA's UK tax exemption does not extend to the IRS.

If you are a US citizen or green-card holder building a portfolio through a UK platform, this is one of the most expensive and most overlooked corners of the US–UK tax code. The good news: once you understand the mechanism, the fix is usually straightforward.

Key takeaways

• Almost every non-US fund is a PFIC. UK OEICs, unit trusts, investment trusts and London-listed ETFs generally meet the IRS income or asset test, so US persons holding them fall inside the PFIC regime.
• A stocks-and-shares ISA is not tax-free to the IRS. The UK wrapper is invisible to the US; the underlying funds are still PFICs and the income is still US-taxable and reportable.
• The default regime is punitive. Without an election, "excess distributions" and gains are taxed at the top ordinary rate with a compounding interest charge for each year you held the fund.
• Form 8621 is required per fund, per year. Reporting obligations can apply even in years with no sale and no distribution.
• The clean-up usually means restructuring. Holding US-domiciled funds, direct shares, or assets inside a treaty-protected pension typically takes you out of the PFIC problem going forward.

What are the PFIC tax rules for US investors abroad?

A foreign corporation is a PFIC if it meets either of two tests: the income test (75% or more of its gross income is passive — interest, dividends, capital gains) or the asset test (at least half of its assets produce, or are held to produce, passive income). A pooled investment fund exists precisely to hold income-producing assets, so nearly all of them qualify.

Congress designed the regime in the 1980s to stop US investors deferring tax by parking money in offshore funds. The mechanism is deliberately unfavourable, and it applies whether the fund sits in a general investment account, an ISA, or an offshore bond. The IRS explains the reporting framework in its guidance for Form 8621 and for international taxpayers generally.

Why is a UK fund or ETF a PFIC?

The trap catches ordinary, sensible investments. A FTSE tracker OEIC, a global equity ETF listed in London, a fixed-income unit trust, an investment trust — each is a non-US corporation whose income is overwhelmingly passive. That is the whole definition of a PFIC.

Crucially, the analysis looks through the wrapper to the asset. UK tax law treats an ISA as exempt and a general account as taxable; US tax law ignores that distinction entirely and asks a single question: is the thing you own a passive foreign corporation? For a fund, the answer is almost always yes. Direct holdings of individual company shares are not PFICs, which is why many US investors in the UK hold single stocks rather than funds.

Is a stocks-and-shares ISA tax-free for US citizens?

No. This is the single most common surprise for US expats in the UK. An ISA shelters growth and income from UK tax, but the US does not recognise the ISA as a tax-favoured account. To the IRS it is simply a container of PFICs.

That means the income and gains inside your ISA are reportable on your US return, the funds are subject to the PFIC regime, and the ISA gives you no US benefit while adding US complexity. Many US persons in the UK are better served — for US purposes — holding cash or individual shares in the ISA, or foregoing it in favour of a structure the US respects. The right answer depends on your wider position, so this is worth reviewing with an adviser before you keep contributing. You can book a consultation to look at your specific holdings.

The three PFIC tax regimes explained

At the heart of the PFIC tax rules for US investors abroad are three ways a PFIC can be taxed. Which one applies depends on whether you make an election and what information the fund provides.

• Excess-distribution regime (Section 1291) — the default. With no election, you are taxed only when you receive an "excess distribution" or sell. The gain is spread back across your holding period, taxed in each prior year at the highest ordinary income rate in force then, and an interest charge is added for the deferral. Long-term capital-gains rates do not apply. The longer you have held the fund, the harsher the result.
• Qualified Electing Fund (QEF, Section 1295). You elect to include your share of the fund's income annually, and capital-gain character is preserved. It is the most favourable regime, but it requires an annual PFIC Annual Information Statement from the fund — which most UK and European fund managers simply do not produce for US shareholders.
• Mark-to-market (Section 1296). Available for marketable stock (typically exchange-traded funds). You report each year's paper gain as ordinary income and take a limited deduction for losses. It removes the interest charge but converts unrealised appreciation into an annual tax bill.

Because QEF statements are rarely available for UK funds, US investors are frequently pushed into either the punitive default regime or mark-to-market. The specific rates, interest computations and any de minimis reporting thresholds change and are fact-specific, so confirm the current figures with a qualified professional before you act — a licensed CPA or Enrolled Agent reviews and signs every position we prepare.

How do I report PFICs on my US return?

Reporting is done on Form 8621, and the obligation is per fund, per year. Hold twelve PFICs and you may owe twelve forms. Filing can be required even in a quiet year — where you received a distribution, disposed of shares, made or maintained an election, or crossed the reporting threshold — not only when you sell.

This is separate from, and in addition to, your FBAR (FinCEN 114) and Form 8938 foreign-asset disclosures, which capture the accounts themselves rather than the PFIC treatment of what is inside them.

If you have held UK funds for years without filing Form 8621, you are not alone, and there is a route back into compliance. Many US expats regularise several missed years at once — see our guide to missed US tax returns and, where the failure was non-wilful, the IRS Streamlined Foreign Offshore Procedure, which is designed for exactly this situation.

How do I clean up a PFIC problem?

Navigating the PFIC tax rules for US investors abroad comes down to a two-part strategy: stop adding to the problem, then deal with what you already hold.

• Going forward, most US investors in the UK move to assets that are not PFICs: US-domiciled funds and ETFs, individual company shares, or investments held inside a pension that the US–UK treaty protects. Your workplace or personal pension is generally not a PFIC problem — the treaty treatment is different, which we cover in our companion guide on US tax on UK pensions and SIPPs.
• For existing holdings, the timing and method of disposal matter, because the interest charge compounds the longer you wait. In some cases a mark-to-market or "purging" election, or a carefully sequenced sale, reduces the eventual bill. These are technical, individual decisions.

Because PFIC calculations depend on your holding period, your other income and figures that change each year, a US–UK expat specialist should model your specific position before you sell anything. Our US–UK expat tax accountants prepare the Form 8621 workpapers, model each regime, and hand a signed, ready-to-file package back to you — with a licensed CPA or EA reviewing every return.

Reviewed by a CPA / Enrolled Agent

This article is general information, not personal tax advice, and PFIC figures and thresholds change. Every return and position we prepare is reviewed and signed by a licensed US professional (CPA or Enrolled Agent). Confirm your own position before acting.

Last updated: 12 August 2026.

Frequently asked questions

Are UK ETFs PFICs for US investors?

Yes. London-listed and other non-US ETFs are foreign corporations whose income is almost entirely passive, so they meet the PFIC definition. Only US-domiciled ETFs and directly held individual shares fall outside the PFIC regime for a US person.

Is a stocks-and-shares ISA tax-free for US citizens?

No. An ISA is exempt from UK tax but the US does not recognise it as a tax-favoured account. The IRS looks through the wrapper to the underlying funds, which are PFICs, so the income and gains remain US-taxable and reportable.

What happens if I never filed Form 8621?

You can usually regularise several missed years together. Where the failure to file was non-wilful, the IRS Streamlined Foreign Offshore Procedure is designed for US expats in exactly this position. A specialist should review your holdings before you file.

How are PFICs taxed without an election?

The default Section 1291 excess-distribution regime spreads your gain back over your holding period, taxes it at the highest ordinary rate for each prior year, and adds an interest charge for the deferral. Long-term capital-gains rates do not apply, so the longer you held the fund, the higher the bill.

How do I avoid PFIC problems as a US person in the UK?

Going forward, most US investors hold US-domiciled funds, individual company shares, or assets inside a treaty-protected pension rather than non-US funds. Existing PFIC holdings should be unwound with professional modelling, because disposal timing affects the interest charge.

Do I file Form 8621 even if I did not sell?

Often yes. Form 8621 can be required per fund, per year — for example where you received a distribution, made or maintained an election, or crossed the reporting threshold — not only in years when you sell. It is separate from your FBAR and Form 8938 filings.