Do I have to file Form 8621 for UK funds held inside a stocks and shares ISA?

Yes. An ISA is a UK tax wrapper, not a separate entity, so for US purposes you are treated as holding the underlying funds directly. Each UK collective fund inside the ISA is tested under section 1297 in its own right and generates its own Form 8621. The UK tax exemption described on the GOV.UK page Individual Savings Accounts (ISAs): Overview has no effect on the US position.

Are direct shares in UK-listed companies PFICs?

Generally no. An operating company such as a bank, retailer or pharmaceutical group does not meet the section 1297 income or asset tests, because its income and assets derive from an active business rather than passive investment. The tests are still applied to the specific company, so a listed entity that has become substantially a holder of investments could fall inside them. Separating direct shareholdings from fund holdings early removes significant work from a filing package.

Does the 25,000 US dollar filing threshold mean I owe no US tax below that level?

No. Regulations section 1.1298-1(c)(2) provides an exception from the annual reporting requirement where the value of all PFIC stock owned directly or indirectly is 25,000 US dollars or less on the last day of the taxable year, or 50,000 US dollars or less for both spouses on a joint return. It is a filing exception only. Section 1291 still applies to distributions and gains, and the exception is unavailable for any year in which you received an excess distribution or recognised gain on a disposition.

Can I make a QEF election on a UK OEIC or unit trust?

Only if the fund provides a PFIC Annual Information Statement. Regulations section 1.1295-1(g) requires that statement to give your pro rata share of the fund's ordinary earnings and net capital gain, or sufficient information for you to calculate it. UK retail fund managers do not normally compute those US figures and have no UK obligation to do so, so for most UK-domiciled funds no QEF election is available in any year. A consolidated tax certificate or reporting fund status data is not a substitute.

Is the mark-to-market election always available as a fallback for UK funds?

No, and this is widely misunderstood. Section 1296 applies only to marketable stock, defined in Regulations section 1.1296-2 as stock regularly traded on a qualified exchange or other market, or stock in certain foreign corporations offering redeemable shares. That second route requires more than 100 unrelated shareholders, public availability at net asset value with no minimum initial investment above 10,000 US dollars, and 90 percent passive income and 90 percent passive assets. Because those percentages exceed the 75 and 50 percent PFIC tests, a fund can be a PFIC and still fail to qualify as marketable stock.

PFIC Reporting UK Funds: Form 8621 Guide

Q: How many Forms 8621 do I file if I hold eight UK funds?

Eight, one for each fund, for every year the reporting requirement applies. The Instructions for Form 8621 state that a separate Form 8621 must be filed for each PFIC in which stock is held directly or indirectly. There is no consolidated schedule for a portfolio, and income and accumulation share classes of the same fund are treated as separate positions.

PFIC reporting UK funds requires a separate Form 8621 for each UK collective investment fund a US person holds, filed annually with the US tax return, and for an accidental American living in Britain that will usually mean every fund inside a stocks and shares ISA as well as every fund in an ordinary general investment account. The form is titled Information Return by a Shareholder of a Passive Foreign Investment Company or Qualified Electing Fund. It is an information return rather than a tax computation, but the regime behind it decides how your fund income and fund gains are taxed in the United States, and the default version of that regime is the least favourable of the three available.

This guide is written for a specific reader: someone born in the United States or to a US parent, who has lived an entirely British financial life, who has accumulated real investment wealth through a platform or an adviser, and who has recently discovered - often through a FATCA questionnaire from a UK bank - that they are a US person. That reader typically holds six to fifteen positions across two or three wrappers, in accumulation share classes, built over a decade of monthly contributions. The reporting problem is therefore not conceptual. It is a data problem, and it drives most of the cost of a catch-up filing package.

What Does PFIC Reporting UK Funds Mean Under Section 1297?

A passive foreign investment company is a non-US corporation that meets either of two tests in Internal Revenue Code section 1297(a). Under the income test, it is a PFIC if 75 percent or more of its gross income for the tax year is passive income. Under the asset test, it is a PFIC if at least 50 percent of the average percentage of assets it held during the tax year are assets that produce passive income or are held for the production of passive income. Only one test has to be met. The Instructions for Form 8621, revised December 2025, state both tests in those terms.

A pooled fund whose entire business is holding shares, bonds and cash meets both tests comfortably. That is the point of the vehicle. Nothing in section 1297 asks whether the fund is well regulated, or whether the investor knew they were American. The classification is mechanical, applied fund by fund, for every year the shares are held. This is why the word accidental carries no legal weight: a UK equity fund bought in 2014 by someone with no idea they held US citizenship is a PFIC for 2014 and every year since. Note also that the analysis attaches to the fund. Your platform is not a PFIC and your ISA is not a PFIC. The individual funds inside them are.

Which of Your UK Holdings Are PFICs and Which Are Not?

For a British investor the map is unusually clean at the edges. The following should be treated as PFICs unless a fund-specific analysis says otherwise, because their income and assets are passive by design.

UK-domiciled open-ended investment companies, commonly sold as OEICs, in both income and accumulation share classes
UK unit trusts, which for these purposes are collective investment funds and are analysed exactly as an OEIC is
UK and Irish domiciled UCITS exchange traded funds, including global and index tracking funds bought on a UK platform
UK-listed investment trusts, which are closed-ended listed companies whose assets are portfolios of securities
Multi-asset and model portfolio funds, which are typically funds of funds and can create exposure at more than one level
Money market and short-term cash funds held as the cash allocation inside an investment wrapper

The following are not PFICs, and separating them out early removes a surprising amount of work from a filing package.

Direct shares in UK-listed operating companies, such as a bank, an oil major, a retailer or a pharmaceutical group, because an active business is not passive
Direct shares in a private UK trading company you own or work for, which raise separate reporting questions but not PFIC questions
Ordinary cash on deposit, including a cash ISA, which is a deposit rather than a fund
Employer share awards settled in shares of a listed operating company
Individual gilts and corporate bonds held directly rather than through a bond fund

Two cautions on that second list. An operating company is not automatically outside the rules; a listed company that has become substantially a holder of investments rather than a trader can fall inside the tests. And the analysis is done at share class level, so an income class and an accumulation class of the same fund are separate positions with separate holding periods, cost bases and distribution histories. A UK pension wrapper works differently again and is outside the scope of this guide.

Does a Stocks and Shares ISA Protect You? The Misconception That Costs Most

It does not. The GOV.UK page Individual Savings Accounts (ISAs): Overview says that you can save tax-free with Individual Savings Accounts, and lists the cash ISA, the stocks and shares ISA, the innovative finance ISA and the Lifetime ISA. That is entirely correct as a matter of UK tax. It is also the most misleading sentence in the life of an accidental American, because the exemption is granted by UK legislation and the United States has never agreed to recognise it. The US-UK income tax treaty contains no article exempting ISA income or ISA gains from US tax.

Structurally an ISA is a wrapper: a set of UK tax rules applied to an account. It is not a separate entity that owns your funds in place of you. For US purposes you look straight through it and see what you would see in a taxable general investment account, a list of foreign fund holdings. Each is tested under section 1297 on its own merits, generates its own Form 8621, and is taxed under one of the three PFIC regimes. The foreign tax credit position is unhelpful too, because no UK tax has been paid on ISA income, so there is nothing to credit against the US liability it creates.

A related misconception is worth killing at the same time. UK reporting fund status is an HMRC classification concerning how a UK investor's returns from an offshore fund are characterised. It is a UK concept and it has no effect at all on whether a fund is a PFIC or on what the IRS requires. Investors frequently arrive believing that because their funds are reporting funds the US position must be tidy. The two are unrelated.

What Does Form 8621 Require, and How Many Do You File?

You file one Form 8621 for each PFIC. The Instructions for Form 8621 are explicit that a separate Form 8621 must be filed for each PFIC in which stock is held directly or indirectly. There is no combined schedule and no consolidation for a portfolio. Ten qualifying funds means ten forms, every year, for as long as the positions are held. This per-fund architecture is why PFIC preparation scales with the number of holdings rather than the size of the portfolio, and why a diversified investor with modest sums in many funds can face a heavier burden than a concentrated one.

Each form identifies the fund and the shareholder, records the share class and number of shares, states the value of the position, then routes into one of several parts depending on the regime. Part I collects the identifying and summary information that all shareholders filing under the section 1298(f) annual reporting rule must complete, and Part II is where elections are made. The real work is not in the form. It is in the workpapers behind it.

Acquisition date and cost for every lot, including every monthly contribution, converted to US dollars
A complete distribution history, including amounts credited to accumulation share classes that were never paid out in cash
The three preceding tax years of distributions, needed to compute the 125 percent average that defines an excess distribution
Every disposal, switch, conversion and rebalance with dates, because each closes a holding period
Year-end fair market value for every position, needed for both the mark-to-market computation and the filing threshold test

Form 8621 is attached to your income tax return and filed by the due date of that return, including extensions. If you are not required to file an income tax return for the year but a Form 8621 obligation still exists, the instructions direct you to file the form directly with the Internal Revenue Service Center, Ogden, UT 84201-0201. That routing matters for the years before an accidental American began filing returns at all.

Who Must File, and Does the De Minimis Exception Help You?

The IRS page About Form 8621, last reviewed on 30 March 2026, lists the circumstances in which a US person who is a direct or indirect shareholder of a PFIC files the form.

Receives certain direct or indirect distributions from a PFIC
Recognises a gain on a direct or indirect disposition of PFIC stock
Is reporting information with respect to a qualified electing fund or a section 1296 mark-to-market election
Is making an election reportable in Part II of the form
Is required to file an annual report pursuant to section 1298(f)

The fifth trigger is the one that catches ordinary UK investors, because it applies simply by holding the shares, with no distribution and no sale required. Against it sits a de minimis exception in Regulations section 1.1298-1(c)(2). On the last day of the shareholder's taxable year, if the value of all PFIC stock owned directly or indirectly is 25,000 US dollars or less, the annual reporting requirement does not apply; on a joint return the figure for both spouses combined is 50,000 US dollars or less. A further exception applies where section 1291 fund stock is only indirectly owned and the value of that stock is 5,000 US dollars or less.

Four features of that exception are routinely misunderstood. First, it is an aggregate test across all PFIC stock, not a per-fund test, so eight small funds are added together. Second, it is measured on the last day of the taxable year, so the answer can flip year to year on market movement alone. Third, it is unavailable for any year in which you received an excess distribution, recognised gain treated as an excess distribution, or have an election in effect. Fourth and most important, it is a filing exception only. It does not switch off section 1291, exempt the income from US tax, or stop holding period exposure accumulating underneath.

What Are the Three PFIC Taxing Regimes?

The default is section 1291, and a PFIC for which no qualified electing fund election and no mark-to-market election has been made is described in the instructions as a section 1291 fund. An excess distribution is the portion of the distributions received in respect of the stock in the tax year that exceeds 125 percent of the average distributions received in respect of that stock during the three preceding tax years. Gain on a disposition of section 1291 fund stock is treated as an excess distribution in full, with no 125 percent cushion. One relief is built in: no part of a distribution received or deemed received during the first tax year of the holding period is treated as an excess distribution.

Once an excess distribution exists it is allocated to each day in the shareholder's holding period. The portion allocated to the current year and to any pre-PFIC years is ordinary income of the current year. The portion allocated to other PFIC years is not included in income at all; it is instead subject to the separate tax and interest charge set out in section 1291(c), computed by reference to the highest rate of tax in effect for each of those earlier years, with interest added as though that tax had been underpaid from then onwards. So the longer a UK fund has been held and the more it has grown, the more of the eventual gain is thrown back into old years and carried forward with interest. Preferential capital gain rates do not apply.

The first alternative is the qualified electing fund election under section 1295. A QEF election makes the fund behave broadly like a US mutual fund: the shareholder includes their pro rata share of the fund's ordinary earnings and net capital gain each year, currently, and the section 1291 throwback and interest charge do not apply to years covered by a valid election. The election must be made by the due date, including extensions, of the shareholder's income tax return for the first tax year to which it will apply.

The second alternative is the mark-to-market election under section 1296. Each year the shareholder includes in income the excess of the fair market value of the stock at year end over their adjusted basis, with a limited deduction available in the other direction, and basis is adjusted accordingly. Amounts are ordinary rather than capital, but the annual mark stops the throwback problem building. The election is made by the due date, including extensions, of the return for the tax year in which the stock is marked to market, and it is available only for stock meeting the definition of marketable stock.

Why Is a QEF Election Usually Unavailable for UK Funds?

Because the election depends on the fund, not on the investor. To make and maintain a QEF election the shareholder needs a PFIC Annual Information Statement from the fund. Regulations section 1.1295-1(g) requires that statement to set out the shareholder's pro rata share of the PFIC's ordinary earnings and net capital gain for the tax year, or sufficient information to enable the shareholder to calculate that pro rata share. Those are US tax concepts. They are not figures a UK fund manager computes in the ordinary course of running a UK-domiciled fund for UK investors, and there is no UK obligation to produce them.

The consequence is blunt. For the great majority of UK retail OEICs and unit trusts no PFIC Annual Information Statement exists for any year, so no QEF election can be made for any year, however much US tax it would save. A consolidated tax certificate is not a substitute, and neither is a fund factsheet or reporting fund status data. Where a manager does produce statements it is usually because the fund has deliberately courted US investors. The way to find out is to ask each manager in writing for the statement for each year in question and keep the reply. Absent it, the position remains a section 1291 fund until disposed of.

Is Mark-to-Market Really Available for an Unlisted UK OEIC?

This is the question most commentary skips. Section 1296 applies only to marketable stock. Regulations section 1.1296-2(a) defines that as PFIC stock regularly traded on a qualified exchange or other market, meaning a national securities exchange registered with the Securities and Exchange Commission, the national market system, or a foreign securities exchange regulated or supervised by a governmental authority of the country in which the market is located. For a UK-listed investment trust or a London-listed exchange traded fund that route is at least analytically available, and the question becomes whether the specific class is regularly traded.

An ordinary UK OEIC or unit trust is not listed and is not traded on an exchange at all. It is dealt at net asset value directly with the manager. Such a fund can only reach marketable stock status through the separate route in Regulations section 1.1296-2(d), covering certain foreign corporations offering redeemable shares. That paragraph imposes conditions stricter than the PFIC tests themselves.

The class must have more than 100 shareholders, excluding shareholders related to each other under section 267(b)
The shares must be readily available for purchase by the general public at net asset value, and the corporation must not require a minimum initial investment greater than 10,000 US dollars
90 percent or more of the corporation's gross income must be passive income
At least 90 percent of its average assets must be assets producing passive income
Regulations section 1.1296-2(d)(2) adds an anti-abuse rule removing marketable status where net asset value is manipulated

Note the asymmetry, because it is the point. A fund becomes a PFIC at 75 percent passive income or 50 percent passive assets, but reaches marketable stock under this route only at 90 percent and 90 percent. There is a real band in between where a fund is unquestionably a PFIC and yet does not qualify as marketable stock, so neither election is open to it. Multi-asset funds with significant property or infrastructure exposure, and institutional classes with high minimum subscriptions, are where this bites. Mark-to-market availability must therefore be evidenced fund by fund and class by class, rather than assumed because the fund is open-ended.

A Worked Scenario: One ISA and One General Investment Account

Consider a reader we will call the London investor. She was born in Chicago while her British parents were on a two-year secondment, returned to the UK aged four, has never worked in the United States and holds a UK passport. In 2026 her bank sent her a FATCA self-certification form asking about US indicia, and she discovered she is a US citizen. She is 44, a senior professional, and holds the following.

A stocks and shares ISA built over eleven years of monthly contributions, holding four UK-domiciled OEICs in accumulation share classes and one London-listed global equity exchange traded fund, worth around 190,000 pounds
A general investment account holding two further UK-domiciled OEICs, one UK-listed investment trust, and direct shares in four FTSE 100 operating companies, worth around 240,000 pounds
A cash ISA and a current account, together around 40,000 pounds

The form count comes first. The four ISA OEICs, the ISA exchange traded fund, the two general account OEICs and the investment trust are eight PFIC positions, so eight Forms 8621 per year. The four direct FTSE 100 holdings generate none, and neither does the cash. The ISA does not reduce the count. If anything it increases the work, because eleven years of monthly contributions into accumulation classes have created a long list of tax lots with no cash distributions to anchor them.

The de minimis exception is then tested. The aggregate value of her PFIC stock on the last day of the year is far above 50,000 US dollars, so it is unavailable, and would have been unavailable in every year since the portfolio passed that level. It would also have been unavailable in any earlier year in which she took a withdrawal, regardless of value.

The regime analysis follows. She asks each manager for PFIC Annual Information Statements. None of the six OEIC managers produce one, so QEF is unavailable for all six in every year and each remains a section 1291 fund. The exchange traded fund and the investment trust are both London-listed, so mark-to-market is analytically available for them going forward, subject to confirming the regularly traded position. For the six OEICs the paragraph (d) route must be tested individually, and at least one multi-asset OEIC is likely to fail the 90 percent conditions. That fund has no election available at all.

The sting arrives in the accumulation share classes. Over eleven years they paid out no cash at all, so in most years there was no excess distribution, which is precisely why nothing ever alerted her. But the growth compounded inside the class, and section 1291 will allocate the whole of the eventual gain back across an eleven-year holding period the moment she sells. A single instruction that looks like an ordinary rebalance can produce a US tax and interest charge referable to years in which she did not know she was American.

What Ordinary UK Investing Activity Counts as a Disposition?

This is the second area where UK investors are caught out, because platform mechanics disguise US taxable events. Under UK rules many of these are unremarkable, and inside an ISA they carry no UK consequence at all, so nothing flags them. For US purposes each of the following closes or resets a holding period and must be captured.

Switching from one fund to another on the platform, which is a sale of one PFIC and a purchase of another, not a continuation
Converting from an income share class to an accumulation class, or from a retail class to a lower-charge class
Automated rebalancing within a model portfolio, which can generate dozens of small dispositions a year without any instruction from you
A fund merger or reconstruction that exchanges your holding for units in a different vehicle
Partial withdrawals and regular drawdowns, which are dispositions of the underlying funds
Transferring an ISA between providers in cash rather than in specie, because the funds are sold and repurchased
Each monthly direct debit contribution, which disposes of nothing but creates a new tax lot with its own holding period

The last point determines how much work a catch-up package involves. Section 1291 allocates over a holding period, and holding periods run per lot. A reader contributing 300 pounds a month into four funds for eleven years has several hundred lots to track before any tax analysis can begin. Platform statements are usually recoverable, but they are denominated in sterling and organised by UK tax year, so they must be converted to US dollars and re-cut to the calendar year before they are usable. Assembling that data early is the single most effective way to control the cost of getting compliant.

How Do PFIC Filings Fold Into a Catch-Up Filing Package?

Form 8621 is not filed on its own in a remediation. It is a component of a complete package and must be internally consistent with everything else in it. For an accidental American coming forward voluntarily the usual route is the IRS Streamlined Foreign Offshore Procedures, which require returns for the most recent three years for which the due date has passed, FBARs for the most recent six years, and a signed certification of non-willfulness. Each Form 8621 attaches to the return for the year it relates to. The same positions also appear on the FBAR through the account holding them and, if thresholds are met, on Form 8938.

There is a further reason not to leave the information return unfiled. Under Internal Revenue Code section 6501(c)(8), where information required under provisions including sections 1295(b) and 1298(f) is not furnished, the period for assessment does not expire before the date which is three years after the date the information is furnished. Unfiled Forms 8621 therefore keep the assessment window open until the information is actually provided. The statute contains a narrowing: if the failure is due to reasonable cause and not willful neglect, the extended period applies only to the item or items related to the failure rather than to the whole return. That narrowing is worth documenting properly when the package is prepared, not arguing for later.

Sequencing matters. The PFIC analysis has to be settled before the returns are drafted, because it drives the income figures, the foreign tax credit position and the certification narrative. Where a position has been held for years under the default regime, moving it out involves purging mechanics covered elsewhere on this site.

PFIC reporting on UK funds is in the end an exercise in reconstruction rather than interpretation. The rules are settled and stated plainly in the Instructions for Form 8621 and the underlying regulations. What is not settled when a reader first comes forward is the factual record: which funds, which classes, which lots, which dates, which values. A preparation team will ask for full transaction histories from first contribution to date, the share class name and ISIN for every line, each manager's written response on the PFIC Annual Information Statement, and 31 December valuations rather than 5 April ones. Building that record accurately is what turns an alarming discovery into a defensible filing package.