Missed Reporting ISA: Seven-Figure ISAs on a US Return

A missed reporting ISA problem at seven figures is fixable. The ISA is tax-free only in the UK. The IRS taxes the dividends and gains inside it, treats most UK funds in it as PFICs needing Form 8621, and expects FBAR and Form 8938 reporting. The Streamlined Foreign Offshore Procedure is usually the way to catch up.

This guide is written for a particular reader: an American who has lived in Britain for many years, or someone who became a US citizen or green card holder more recently, and who has filled a stocks and shares ISA every tax year since the wrapper was created. After twenty-odd years of full subscriptions, reinvested dividends and steady markets, that ISA can easily be worth more than £1 million. It holds UK unit trusts and OEICs, a spread of investment companies, and a portfolio of directly held shares. None of it has ever appeared on a US return. At this size the problem looks different from the small-balance version described in most online guides. There are more forms, the interest charges are larger, and there is little room for rough estimates.

Why is an ISA not tax-free on a US return?

The Individual Savings Account is a creature of UK statute. HMRC exempts income and gains inside it from UK income tax and capital gains tax, and the annual subscription allowance is currently £20,000 (see the government's ISA guidance on gov.uk). The United States taxes its citizens and green card holders on worldwide income, wherever they live, and US law gives UK tax-free status no recognition of any kind.

The US-UK income tax treaty does not help either. Its saving clause keeps the US right to tax its own citizens as if the treaty did not exist, apart from a short list of exceptions. Ordinary investment accounts are not among them, and an ISA is an ordinary investment account. For US purposes it is a UK brokerage account. You are treated as owning each fund unit and share inside it directly, and every dividend, interest payment and disposal is reportable in the year it happens.

That leaves a double disadvantage. The ISA shelters you from UK tax, so there is no UK tax to credit against the US liability, and the foreign tax credit that normally stops double taxation for Americans in Britain has nothing to offset. The Foreign Earned Income Exclusion only covers earned income, so it cannot shelter investment returns. The 3.8% Net Investment Income Tax can also apply on top of ordinary rates once your income is above the thresholds.

What sits inside a seven-figure ISA, and why the mix matters

The first job in any catch-up is to split the holdings into categories, because each category is taxed differently in the US. A mature ISA usually holds three kinds of asset.

UK open-ended funds: unit trusts and OEICs

Almost every UK-domiciled pooled fund is a Passive Foreign Investment Company (PFIC) under IRC section 1297. A fund meets the income test (75% or more passive income) or the asset test (50% or more passive assets) almost by definition. Tracker funds, active equity funds, bond funds, multi-asset funds and money-market funds held inside the ISA are all very likely to be PFICs. Accumulation units are no safer than income units, because retained income does not change the classification.

Investment trusts and investment companies

London-listed investment companies are UK corporations whose business is holding a portfolio, so they usually meet the PFIC tests as well. Because they are exchange-listed, they are often the easiest holdings to fit into a mark-to-market computation (discussed below). Some listed vehicles hold operating businesses or real assets, and those need a separate look. Private equity, infrastructure and property structures can come out differently, and each should be classified from its own accounts, not assumed.

Directly held shares in UK and overseas trading companies

Shares in ordinary operating companies, such as FTSE-listed banks, miners, consumer goods groups and industrials, are generally not PFICs. They are taxed under the normal rules. Dividends from UK companies are usually eligible to be qualified dividends taxed at preferential capital gains rates, because the UK treaty makes UK companies qualified foreign corporations. Disposals produce ordinary short- or long-term capital gains, calculated in US dollars. For a seven-figure ISA, the proportion held in direct shares often decides whether the catch-up is a manageable task or a major PFIC reconstruction.

How does the PFIC excess distribution regime hit a large, long-held ISA?

If no election is made, each PFIC is taxed under section 1291, the excess distribution regime. The rules are mechanical and harsh, and their effect grows with the length of time the fund has been held.

• Excess distributions. Distributions in a year that exceed 125% of the average of the previous three years' distributions are "excess". Many funds pay steady income and never trigger this. Accumulation funds and funds with irregular payouts can.
• Gains on sale. Every gain on disposing of PFIC units is treated in full as an excess distribution, even after decades. It is never capital gain and never gets preferential rates. Losses are generally not deductible under the default regime.
• Allocation across the holding period. The excess amount is spread day by day across your holding period. The part allocated to the current year, and to any years before the fund was a PFIC in your hands (for example, before you became a US person), is taxed as ordinary income this year. The part allocated to each earlier year is taxed at the highest individual rate in force in that year, whatever your actual bracket was.
• Interest charge. An interest charge applies to the deferred tax for each earlier year, at the IRS underpayment rate, compounded, from that year's due date to the current due date.

Consider an illustration, with figures rounded and used only to show the mechanics. A fund was bought inside the ISA in 2008 for £80,000 and switched to another fund in 2024 for £310,000. Any switch or sale inside an ISA counts as a US disposal. The US gain, worked out in dollars at the exchange rate on each date, is spread over roughly sixteen years. Most of it is taxed at the top rate in force for each year it is allocated to: 35% for 2008 to 2012, 39.6% for 2013 to 2017 and 37% since 2018. Compounded interest for up to fifteen years is then added. The total US charge on that single switch can take a very large share of the gain. In a portfolio that has been rebalanced for twenty years, the same thing has happened on dozens of switches that nobody reported.

This is why the reconstruction has to be complete. Excess distribution computations depend on the full acquisition history of each fund: every purchase lot, every reinvested distribution and every partial sale, going back to the first purchase and not only to the start of the catch-up window. Current-year figures cannot be computed properly without the history behind them.

Can you still make a QEF or mark-to-market election late?

This is where a large ISA is most different from a small one. Both elections exist to get out of section 1291, and both are much harder to use retroactively.

The Qualified Electing Fund (QEF) election

A QEF election taxes your share of the fund's ordinary earnings and net capital gain each year, with capital gains keeping their character. It needs a PFIC Annual Information Statement from the fund. Most UK retail funds have never produced one for US investors. Even where a statement exists, a QEF election is normally due with a timely filed return for the first year the fund is held. A retroactive QEF election generally needs IRS consent under the regulations, usually through a private letter ruling. That means showing reasonable reliance on a qualified tax professional and that the government's interests are not prejudiced. For most catch-up clients it is not realistic, and where it might be, the cost of the ruling request has to be weighed fund by fund.

The mark-to-market election

Under section 1296, a mark-to-market election is available for "marketable stock". This includes stock regularly traded on a qualified exchange, such as the London Stock Exchange, and under the regulations can extend to certain foreign funds that publish a net asset value and redeem at it. You include each year's rise in value as ordinary income and deduct falls to the extent of earlier inclusions.

Unlike a QEF election, mark-to-market can be made for a later year without IRS consent. But when the election starts after the first year of your holding period, a coordination rule applies. For the first election year, the gain is taxed under section 1291 as if you had sold at year end, with the full top-rate tax and interest charge on the history built up to that point. Mark-to-market stops future damage but does not undo past damage. In a long-held ISA, the first-year hit on each fund is often the largest single item in the catch-up.

Why the "right" answer differs fund by fund

With twenty or thirty PFICs, the choice is rarely the same for all of them. A fund with a small unrealised gain may be cheap to bring into mark-to-market now. A fund that has already been sold stays under section 1291 regardless. An investment company with a large embedded gain may justify a detailed comparison of timing, including whether a disposal and reinvestment into direct shares is better than electing. The aim of the preparation work is to model each holding, not to apply one approach to everything.

Form 8621 at scale: what the filing actually looks like

Form 8621 is filed per PFIC, per year, attached to the 1040. With a seven-figure ISA, the $25,000 aggregate de minimis exception (or $50,000 on a joint return) almost never applies. A catch-up covering three years for a portfolio of 25 funds and investment companies means around 75 separate Forms 8621. Each has its own dollar-denominated basis history, distribution record, election status and computation. See the IRS's page About Form 8621 for the current form and instructions.

Two more points matter at this size. First, a missing Form 8621 keeps the assessment statute open for the whole return, under the rule for missing international information returns, not just for the PFIC items. Second, ISA managers issue no US tax documents at all: no 1099s, no PFIC statements and no dollar figures. Everything comes from annual statements, contract notes and transaction histories, converted at the correct rates. Where records are missing for older years, the gap has to be filled with care and the approach documented.

Dividends, interest and gains on the Form 1040

Outside the PFIC holdings, the rest of the ISA goes onto the ordinary schedules.

• Dividends from direct shares go on Schedule B and are usually qualified if the holding-period test is met. Scrip dividends, special dividends and return-of-capital events each need their own treatment.
• Interest on cash held in the ISA is ordinary income. With large cash balances waiting to be invested, this can add up.
• Disposals of direct shares go on Form 8949 and Schedule D, with basis and proceeds converted to dollars on the trade dates. The dollar gain can differ a great deal from the sterling gain. A share that is flat in pounds can show a US gain or loss purely from currency movement.
• Corporate actions such as takeovers for cash, demergers and share-for-share exchanges must each be analysed under US rules. UK treatment is irrelevant because the ISA ignored them for UK purposes.

Because there is no UK tax on any of this, there is no foreign tax credit to claim against it. Excess foreign tax credits carried forward from UK-taxed income, such as salary or bonuses, may still be available. Those need to be tracked across the whole catch-up period so they are not wasted.

FBAR and Form 8938 for the ISA account

An ISA is a foreign financial account. It counts towards the FBAR threshold (aggregate foreign account balances above $10,000 at any time in the year) and has to be listed on FinCEN Form 114 with its maximum value. At seven figures it also exceeds the Form 8938 thresholds for filers living abroad by a wide margin: $200,000 at year end or $300,000 at any time for a single filer, and $400,000 or $600,000 for joint filers. See the IRS's page About Form 8938.

The two filings overlap but neither replaces the other. FBAR goes to FinCEN and Form 8938 goes with the 1040. An unfiled Form 8938 carries its own penalty, starting at $10,000, and also keeps the statute open. Non-wilful FBAR penalties, now assessed per report rather than per account following the Supreme Court's decision in Bittner, are inflation-adjusted amounts above $10,000 per year. Across several years and a large balance, the potential exposure is significant, which is the main reason to choose the disclosure route carefully. Our FBAR penalty calculator gives a first view of the range.

How does the Streamlined Foreign Offshore Procedure fix a missed reporting ISA?

For a US person resident in the UK whose failure was non-wilful, which usually means they genuinely did not know that a UK tax-free account was taxable in the US, the Streamlined Foreign Offshore Procedure (SFOP) is usually the right route. The IRS sets out the terms on its page for US taxpayers residing outside the United States.

• Non-residency test. In at least one of the three most recent tax years, you must have had no US abode and been physically outside the US for at least 330 full days. Long-term UK residents normally meet this easily.
• Three years of returns. Delinquent or amended Forms 1040 for the three most recent years whose due date (including extensions) has passed, with every required Form 8621, Form 8938 and supporting schedule.
• Six years of FBARs. The six most recent years for which the FBAR due date has passed. If a year's extended FBAR deadline has not yet passed, that year is simply filed on time.
• Certification. Form 14653 is a signed statement of the facts showing why the failure was non-wilful. For a large ISA it needs to be specific and credible, not boilerplate.
• Payment. Tax and statutory interest for the three years is paid with the submission. Under SFOP the miscellaneous offshore penalty is zero, and no FBAR or information-return penalties are asserted on accepted submissions.

A seven-figure balance does not by itself make a failure wilful. But the IRS reads the certification against the facts, so a history of US filing, professional advice received, or earlier awareness of FATCA letters from an ISA manager all need to be addressed openly. If the facts do not support non-wilfulness, the streamlined route is not available and other options need to be considered first. Our IRS streamlined filing team assesses this before any work on the return starts.

The PFIC wrinkle inside a streamlined submission

Streamlined limits the returns you file to three years. It does not limit the PFIC maths. The excess distribution computations for those three years still depend on the full acquisition history of each fund, going back twenty years or more in some cases. Any mark-to-market elections made in the catch-up years will trigger their first-year section 1291 coordination charge inside the submission. Deciding which funds to elect for, which to sell, and in what order, is part of the preparation, not something to leave until afterwards.

A practical sequence for the catch-up

1. Confirm US status and dates. Establish exactly when US citizenship or green card status started. Holdings bought before that date are treated differently under the PFIC allocation rules, which can be a significant saving for a recently naturalised citizen or recent green card holder.
2. Collect the full ISA record. Get annual statements, transaction histories and contract notes from the start. For accounts transferred between managers, get the transfer valuations and the underlying lot history.
3. Classify every holding. Sort holdings into PFIC funds, PFIC investment companies, non-PFIC trading shares and cash. Borderline listed vehicles need individual review.
4. Rebuild in dollars. Convert basis, distributions and proceeds at the correct historic rates, lot by lot.
5. Model each PFIC. Compare staying under section 1291, electing mark-to-market with its first-year charge, and disposal. Assess whether a retroactive QEF approach is worth considering in any particular case.
6. Prepare the submission. This means three years of 1040s with all Forms 8621 and 8938, six years of FBARs, and a fact-specific Form 14653 certification.
7. Get current and stay current. File the current year on time, with the elections in place, and set up an annual process so the ISA is reported every year from now on.

What about the UK side?

HMRC is not the problem here. Held properly, the ISA stays fully tax-free in the UK, and nothing in a US catch-up changes that. Two UK points still matter. First, UK ISA managers are reporting financial institutions under the US-UK FATCA agreement. They identify US persons and report their accounts to HMRC, which passes the information to the IRS. The IRS may therefore already hold data on the account, which is a good reason to deal with it before the IRS writes to you. Second, any decision to sell PFIC funds inside the ISA and reinvest in direct shares is neutral in the UK. There is no UK CGT inside the wrapper, so restructuring for US reasons costs nothing in UK tax.

How Jungle Tax prepares a seven-figure ISA catch-up

Jungle Tax prepares US and UK returns for internationally mobile families, founders and executives. For a large ISA, that means rebuilding every fund from its first purchase, preparing each Form 8621 with computations we can defend, and assembling a streamlined submission with a non-wilful certification that stands up to scrutiny. Our US-UK tax accountants work regularly with high-net-worth clients whose UK investment histories were never designed with the IRS in mind. For wider reading, see our library of cross-border tax guides.

If you hold a substantial ISA that has never appeared on a US return, the time to act is before the IRS contacts you, not after. Speak to us in confidence and contact our cross-border team to arrange a private consultation. We will review your holdings, confirm your filing position and give you a clear, fixed plan to bring every year into compliance.