UK ISAs for US Citizens: PFIC Rules, FBAR and What to Do Instead (2026)

An Individual Savings Account is a UK statutory wrapper. Inside it, HMRC charges no income tax on interest or dividends and no capital gains tax on growth. That exemption exists in the UK Income Tax (Trading and Other Income) Act and the ISA Regulations 1998. It does not exist anywhere in the Internal Revenue Code. The United States taxes its citizens and green card holders on worldwide income, wherever they live. The only thing that can switch off that rule is a treaty provision that survives the saving clause in Article 1(4) of the US-UK income tax treaty. The treaty has no ISA article. An ISA is not a pension scheme under Article 3(1)(o) because it has no retirement restriction, so Article 18 does not protect its growth, and Article 17 does not protect its withdrawals. The IRS simply looks through the wrapper and taxes what is inside it. That leaves three separate problems, and most people only know about the first: - Everything the ISA earns is US taxable income in the year it arises: interest, dividends, fund distributions, the Lifetime ISA bonus. - If the ISA holds UK or European funds, each fund is a Passive Foreign Investment Company (PFIC), with its own punitive tax regime and its own form. - The ISA is a foreign financial account, so it goes on the FBAR and usually on Form 8938 whether or not it produced any income. There is no foreign tax credit to soften this. Form 1116 only offsets foreign tax actually paid, and the UK charges nothing on an ISA. The 3.8% Net Investment Income Tax applies on top above $200,000 of modified adjusted gross income (single) or $250,000 (joint), and since the Federal Circuit's August 31, 2026 decisions reversing Christensen and Bruyea there is no realistic treaty argument for crediting UK tax against it. None of this means you must never hold an ISA. It means you must choose what goes inside it with the IRS in mind, and report it correctly every year.

The wrapper is irrelevant to the IRS. What matters is the asset inside it. Here is the treatment for each ISA type, assuming the holder is a US citizen or green card holder. - Cash ISA. Interest is ordinary income on Schedule B, converted to dollars at the rate when credited or a reasonable annual average. FBAR and Form 8938 apply. No PFIC issue. From April 6, 2027 the cash ISA limit falls to £12,000 for savers under 65, with the remaining £8,000 of the £20,000 allowance reserved for stocks and shares. - Stocks and Shares ISA holding UK funds. Every OEIC, unit trust, UCITS ETF or investment trust inside the account is a PFIC. Each one needs its own Form 8621 every year, and each is taxed under the Section 1291 excess distribution regime unless you make an election. This is the ISA that does the real damage. Dividends and distributions from the funds are also reported currently. - Stocks and Shares ISA holding individual shares. Shares in an operating company such as Shell, Unilever or Apple are not PFICs. Dividends go on Schedule B, usually at qualified dividend rates for UK companies, and gains on sale are ordinary capital gains on Form 8949 and Schedule D, long-term after one year. No Form 8621. A UK REIT or a cash-heavy holding company can itself be a PFIC. - Innovative Finance ISA. Peer-to-peer interest is ordinary income on Schedule B. A defaulted loan is usually a nonbusiness bad debt, a short-term capital loss when it becomes wholly worthless. - Lifetime ISA. You can pay in £4,000 a year and the government adds a 25% bonus, up to £1,000. The bonus is US taxable income in the year it is credited. If the account holds funds, they are PFICs. The 25% government withdrawal charge on a withdrawal before age 60 that is not for a first home is a penalty, not a tax and not a loss, so it is not deductible and not creditable. The government opened a consultation on June 23, 2026 to replace the Lifetime ISA, with a successor product expected around April 2028. - Junior ISA. The child owns the account, so the child has the tax problem. If the child is a US citizen, fund holdings are the child's PFICs, reported on the child's own return or on a parent's return via Form 8814 where eligible. Unearned income above the kiddie tax threshold, roughly $2,800 in 2026, is taxed at the parents' marginal rate. The child files their own FBAR if their foreign accounts exceed $10,000 in aggregate, with a parent signing. - Help to Buy ISA. Closed to new savers since November 30, 2019, but existing holders can contribute until November 30, 2029 and claim the bonus until December 1, 2030. Interest is taxable each year. The bonus, up to £3,000, is US income when paid at completion. The single most important sentence in this guide is this: a Stocks and Shares ISA that holds funds is the problem, and a Stocks and Shares ISA that holds individual shares is not.

Some preparers file Form 3520 and Form 3520-A for every ISA, on the theory that a UK savings wrapper administered by an ISA manager is a foreign trust. The majority view among cross-border practitioners, and our position, is that it is not. An ISA is an account. You own the cash or investments directly, the ISA manager is a custodian under the ISA Regulations, and no separate entity holds property for a beneficiary. That is a custodial arrangement, not a trust under Treasury Regulation 301.7701-4. A Junior ISA is closer to the line because the child cannot access the money until 18, but it is still held in the child's name with the parent as registered contact, not as trustee. Rev. Proc. 2020-17 does not help if you take the trust view: its non-retirement category covers only medical, disability and educational savings trusts. Because we do not take that view, we do not file Form 3520 for a Cash, Stocks and Shares, Innovative Finance or Lifetime ISA. If you have been filing them, you can stop. The prior filings are harmless.

A Passive Foreign Investment Company is any non-US corporation where 75% or more of gross income is passive, or 50% or more of assets produce passive income. Every pooled investment fund meets that test, so every UK OEIC, unit trust, UCITS ETF and investment trust is a PFIC. It does not matter that the fund tracks the S&P 500 or is run by Vanguard. What matters is where the fund is domiciled. You report each PFIC on its own Form 8621, attached to Form 1040, every year you hold it. There are three ways a PFIC can be taxed. The default is the worst.

If you hold UK funds inside an ISA, the question is not whether to fix it but how quickly and in what order. The tax has already accrued. Every additional year adds another year of 37% throwback and compound interest. Step one: list every holding with purchase date and cost. Mark which are PFICs (any fund) and which are not (individual shares), and which PFICs are exchange-listed and therefore eligible for mark-to-market. Step two: sell the PFICs. A sale is a disposition, so each fund needs a Form 8621 with the Section 1291 computation for the year of sale. Selling now is almost always cheaper than selling later. A fund standing at a loss produces an ordinary capital loss, not an excess distribution, and that loss can offset gains on individual shares or other capital gains on Schedule D. It cannot offset the deferred tax and interest on the winning PFICs, which is exactly why you want the winners out before the gains grow. Step three: decide what replaces them. In rough order of preference for a US citizen in the UK: - Individual shares inside the same ISA. No PFIC, HMRC-free, only Schedule B and Schedule D in the US. The cost is concentration risk and the work of running a portfolio of single names. - US-listed ETFs in a UK General Investment Account. No PFIC because the fund is US domiciled, and no UK tax problem if you choose funds with HMRC reporting fund status, which most large Vanguard, iShares and SPDR US ETFs have. Gains are taxable in both countries but the Foreign Tax Credit works normally. - US-listed ETFs in a SIPP. UK tax relief on the way in and, once you claim Article 18(1) on Form 8833, US deferral on growth. The PRIIPs barrier below applies to SIPP platforms too. - A US brokerage account. Some US brokers accept UK-resident clients and sit outside the UK KID rules. UK tax and the reporting fund point still apply. - London-listed investment trusts or UCITS ETFs with a mark-to-market election, if the money must stay inside an ISA and you cannot pick single shares. Ordinary income on growth each year, but no interest charge. Step four: keep the Cash ISA if it suits you. Interest is US taxable, but there is no PFIC problem. On timing: if you are about to move to the US, sell the PFICs while still UK resident. The UK result is the same (nothing) and you avoid state income tax on the gain. If you are giving up citizenship or a long-held green card, run the exit tax numbers before selling.

UK platforms will not sell a US-domiciled ETF to a retail investor because the fund publishes no Key Information Document under the retained EU PRIIPs Regulation. The FCA is replacing PRIIPs with its Consumer Composite Investments regime, but as of September 2026 it has not extended equivalence to US-registered funds, which remain unregulated collective investment schemes for UK purposes. Vanguard and iShares have no reason to produce UK KIDs for their US ETFs, so the barrier stays. Five practical routes around it: - Open an account with a US brokerage that accepts UK residents. Several large US firms onboard UK-resident US citizens through their international divisions, outside FCA retail rules. - Elect professional client status with a UK broker. You must meet two of three tests: a portfolio above 500,000 euros, at least 10 significant trades a quarter over the past four quarters, or a year of relevant work in financial services. You give up some FCA protections, including most Financial Ombudsman rights. - Use a US-expat-focused UK wealth manager that has arranged professional client access for its SIPP and GIA clients. - Buy individual US shares. A share is not a packaged product, so no KID is needed. This works for equities, not for bond exposure. - Hold UCITS ETFs and elect mark-to-market. The fallback if none of the above is available. A managed PFIC problem, not a solved one. Whichever route you take, check the HMRC reporting fund list before buying a US ETF. A non-reporting fund's gain is taxed in the UK as income at up to 45% rather than as a capital gain at 24%, which swaps a US problem for a UK one.

This is the most common situation we see, and it is fixable. Most Americans in the UK who opened a Stocks and Shares ISA did so on the advice of a UK adviser who had never heard of Form 8621. The IRS knows this, and there is a route that removes penalties. If you live outside the US and the failure was non-willful, the Streamlined Foreign Offshore Procedures let you file the last 3 years of returns and the last 6 years of FBARs, pay the tax and interest, and pay no penalties. Not knowing that a UK ISA was US-reportable is the textbook non-willful fact pattern. Inside the package, each PFIC needs a Form 8621 for each of the 3 years, with the Section 1291 computation for any distributions or sales. If you still hold the funds, the tax on the unrealised gain is not yet due, but the clock is running. Most people sell in the year of the streamlined filing or the year after, and the throwback is computed from the original purchase date, not from the start of the 3-year window. If you live in the US, the Streamlined Domestic Offshore Procedures apply instead, with a 5% penalty on the highest year-end balance of the unreported accounts. If your conduct might be seen as willful, do not use streamlined. Speak to a tax attorney about the Voluntary Disclosure Practice first. One warning. Some preparers "clean up" old PFIC years by filing a mark-to-market election on a late Form 8621 without the deemed-sale computation. That is not a valid election and it leaves the Section 1291 exposure in place.

Every ISA is a foreign financial account. Here is what a US citizen in the UK files, and when. - FBAR (FinCEN Form 114). Required if the combined maximum value of all your foreign accounts, including every ISA, bank account, SIPP and Premium Bonds holding, exceeded $10,000 at any point in the year. Filed with FinCEN, due April 15 with an automatic extension to October 15. Report each ISA separately at its maximum value, converted at the Treasury year-end rate. - Form 8938. Required with Form 1040 if your specified foreign financial assets exceed $200,000 at year end or $300,000 at any time for a single filer living abroad, or $400,000 at year end or $600,000 at any time for joint filers living abroad. Thresholds for US residents are far lower: $50,000 and $75,000 single, $100,000 and $150,000 joint. ISAs count. Individual shares held in an ISA are reported through the account, not separately. - Form 8621. One per PFIC per year. The de minimis exception lets you skip the annual form if all your PFICs together are worth $25,000 or less at year end, $50,000 on a joint return, and you had no excess distribution, no sale at a gain and no election in place. It removes the form, not the tax. The statute of limitations on your entire return stays open while a required Form 8621 is missing. - Schedule B. Interest and dividends from every ISA in dollars. Answer yes to the foreign account questions in Part III and name the United Kingdom. - Form 8949 and Schedule D. Sales of individual shares inside an ISA. Convert cost and proceeds separately at the rates on the purchase and sale dates. Currency movement is part of the gain or loss. - Form 8960. Net Investment Income Tax if your modified AGI exceeds $200,000 single or $250,000 joint. ISA interest, dividends and gains are all net investment income. No treaty credit is available. - Form 3520 and 3520-A. Not required for an ISA on the majority view described above. - Form 8833. Not needed. There is no treaty position to disclose because no treaty article applies to an ISA. Keep ISA statements, contract notes and dividend vouchers for at least 6 years. A future Section 1291 computation needs the original purchase date and cost, and ISA managers do not keep records forever.