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HorizonUK Tax Solutions

US-UK Tax

Can Americans in the UK have an ISA?

Answered by Jordan Onraet-Wells, Founder & Chartered Tax Adviser (CTA). Published 9 August 2026. Last reviewed 9 August 2026.

The short answer

Yes. Nothing in UK law stops a US citizen who is UK resident from opening or holding an ISA: eligibility turns on UK residence, not nationality, and HMRC treats the account as fully tax-free with the normal £20,000 subscription limit for 2026/27. The catch sits entirely on the American side. The US does not recognise the ISA wrapper, so the interest, dividends and gains inside it remain taxable on the US return, and the UK or EU funds typically held in a stocks and shares ISA are usually PFICs with some of the most punitive treatment in the US tax code.

  • ISA eligibility is residence-based, not nationality-based, so an American resident in the UK can open one and the UK side works exactly as it does for anyone else.
  • The treaty saving clause lets the US tax its citizens as if the treaty did not exist, so for US purposes an ISA is just an ordinary taxable account.
  • Because the UK charges nothing on ISA income and gains, there is no UK tax to credit against the US bill on the same income.
  • UK unit trusts, OEICs and most UK and EU listed ETFs inside a stocks and shares ISA are usually PFICs, and each fund generally needs its own Form 8621.
  • An ISA also counts towards the FBAR and FATCA reporting thresholds like any other UK account.

You can open one, and the UK side works perfectly

ISA rules ask where you live, not what passport you hold: GOV.UK requires you to be UK resident to subscribe (or a Crown servant or member of the armed forces, or their spouse or civil partner, if living abroad), with no nationality restriction. An American who is UK resident can therefore subscribe up to £20,000 in 2026/27 across cash, stocks and shares, innovative finance and Lifetime ISAs, and HMRC treats everything inside as free of UK Income Tax and Capital Gains Tax, exactly as it does for any other saver. Nothing inside the wrapper goes on a UK Self Assessment return. The question is never whether you can hold an ISA; it is what the account costs you on the other side of the Atlantic.

Why the wrapper fails on the US side

US law contains no equivalent recognition of the ISA, and the US-UK treaty does not create one: its saving clause reserves the right of the US to tax its own citizens and green card holders largely as if the treaty did not exist. So for US purposes a cash ISA pays taxable interest and a stocks and shares ISA produces taxable dividends and gains, all reportable on the US return, with the account counting towards FBAR and FATCA thresholds like any other UK account. The trap is one-sided in the worst way: because the UK charges nothing, there is no UK tax to credit against the US bill, so the US tax stands in full. A US person can pay more total tax on income inside an ISA than a UK-only saver pays on nothing at all.

The PFIC layer makes it worse

Most platforms populate stocks and shares ISAs with UK unit trusts, OEICs and UK or EU listed ETFs, and for a US person those funds are generally Passive Foreign Investment Companies. Under the default section 1291 regime, gains and large distributions are spread over the holding period, taxed at the highest rates in force for those years with an interest charge added, and each fund generally needs its own Form 8621 every year. Direct shareholdings in individual operating companies and ordinary cash deposits generally sit outside the PFIC rules, though the income is still US-taxable. None of this is investment advice: we describe how the account and fund types are taxed, not what anyone should hold, and US filings such as Form 8621 are handled by our US partners (Enrolled Agents and CPAs), whom we coordinate for you. Our full guide to the PFIC and ISA traps covers the detail, and Horizon works on fixed fees agreed upfront, with a free clarity call at /book if you are a US person with an ISA already open.

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Sources and further reading

This is general information for the 2026/27 UK tax year, not personal tax advice; speak to a Chartered Tax Adviser about your own position.

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