Missed Reporting Investment Account: Sterling Cash Fund PFICs

A missed reporting investment account often contains a PFIC nobody noticed: the sterling money market or liquidity fund used as the cash sweep. To the IRS it is a foreign fund, not cash. Each one generally needs Form 8621 for every year held, and unreported years are corrected through a catch-up filing.

This guide is for US citizens and green card holders living in the UK whose wealth platform, private bank or discretionary portfolio parks uninvested cash in a sterling money market fund. It is the holding that most often survives an otherwise careful review. Clients who have deliberately avoided UK equity funds, and who know the PFIC rules well, still describe this line on their statement as cash. At Jungle Tax we prepare the US and UK returns that put this right, and this guide explains precisely how the rules apply to cash-like funds, which behave differently from equity funds under every one of the three PFIC regimes.

Why is a sterling money market fund a PFIC?

A foreign corporation is a passive foreign investment company for any year in which 75% or more of its gross income is passive, or 50% or more of its assets by value produce passive income. A money market fund is the purest possible case. Its income is interest on deposits, commercial paper, certificates of deposit and short-dated government bills. Its assets are those same instruments. It meets both tests at or near 100%, every year, with no borderline analysis required.

The points that cause the oversight are about presentation, not law:

• It is labelled as cash. Platform valuations commonly show the fund under a cash or liquidity heading, alongside genuine bank balances.
• It is bought automatically. Sweep arrangements move sale proceeds, dividends and new deposits into the fund without an instruction, so the client never places a trade.
• It does not move in price. A stable-value share class is priced at or very close to one pound, so it does not look like an investment.
• The US has special rules for its own money market funds. Simplified US methods for money market fund shares were written for funds registered and regulated in the United States. A fund domiciled in the UK, Ireland or Luxembourg does not benefit from them.

A genuine bank deposit, a fixed-term deposit and a directly held Treasury bill or gilt are not PFICs. The distinction is between holding a debt instrument yourself and holding shares in a foreign company that holds them for you. Only the second is a fund.

Each sub-fund and share class matters

Liquidity funds are usually sub-funds of an umbrella company, and each sub-fund is generally treated as a separate corporation for US purposes. A portfolio with a sterling sweep, a US dollar liquidity fund and a short-dated bond fund used as enhanced cash therefore holds three PFICs, not one. Where a discretionary manager switched share classes or sub-funds over the years, each is traced separately.

Does a cash fund really need Form 8621 every year?

In general, yes. A US person who is a shareholder of a PFIC files a separate Form 8621 for each PFIC with the annual Form 1040, whether or not anything was sold. The form is an information return and a tax computation in one. For a cash fund it reports the year-end value, the distributions received, any redemptions, and the regime under which the holding is taxed.

What are the de minimis thresholds, and why are they usually exceeded?

There is a narrow exception from the annual report for a fund taxed under the default regime. It applies where:

• the value of all PFIC stock the shareholder owns is $25,000 or less on the last day of the tax year, or $50,000 or less on a joint return; and
• the shareholder did not receive an excess distribution, and did not recognise gain on a sale or redemption, in that year.

A separate $5,000 limit applies to a PFIC owned indirectly through another PFIC. For cash funds held by wealthy clients, the exception fails for four reasons.

1. The limit is aggregate. It counts every PFIC in every account, not each fund separately. A sweep balance held after a property sale, a bonus or a liquidity event is routinely many multiples of the limit on its own.
2. It is tested at year end. Cash is often highest on 31 December, when portfolios are being repositioned.
3. Accumulating classes produce gain on every redemption. Each time the platform sells units to fund a purchase or a withdrawal, there is a disposal at a gain, which removes the exception for that year.
4. Distributing classes produced excess distributions when rates rose. This is explained below, and it caught almost every long-standing holder.

Two further points are routinely misunderstood. The exception removes only the annual reporting requirement; it does not exempt the income from tax. And it is designed for funds under the default regime, so it does not help where a mark-to-market or QEF election is in place, when the form is required to report the election's annual result.

How do the three PFIC regimes behave for a cash fund?

Our general guides cover the regimes for equity funds. A cash-like fund produces different, and sometimes surprising, results under each.

Regime	Distributing, stable-value class	Accumulating class	Practical note for cash funds
Excess distribution (section 1291, the default)	Distributions are ordinary, non-qualified dividends. Any amount above 125% of the prior three-year average is an excess distribution. Redemption gain is usually only currency gain.	No annual US income. All accrued interest emerges as gain on redemption, and the whole gain is treated as an excess distribution.	Applies automatically to every unreported year. Tax is often modest; the computation is not.
Mark-to-market (section 1296)	Distributions taxed as ordinary dividends. Year-end mark in US dollars reflects only exchange-rate movement.	Year-end mark captures accrued interest plus exchange-rate movement, all as ordinary income.	Only for marketable stock. Loss deductions are capped at prior inclusions. Not retroactive.
Qualified Electing Fund (section 1295)	Share of ordinary earnings taxed annually, broadly matching interest earned. Distributions of previously taxed income are not taxed again.	Same annual inclusion, with basis increased so redemption gain is largely eliminated.	Economically the best fit, but requires a PFIC Annual Information Statement, which sterling cash funds rarely supply.

Excess distribution: the interest-rate trap in distributing classes

Under the default rules, a distribution is an excess distribution to the extent that total distributions received in the year exceed 125% of the average received in the three preceding years, or in the shorter period the shares have been held. Nothing received in the first year of the holding period is an excess distribution.

For an equity fund with steady dividends this test is rarely failed. For a cash fund it was failed almost universally when sterling interest rates rose from near zero. Consider a holding of roughly £800,000 in a distributing class held since January 2020, illustrated in sterling for simplicity:

Year	Distributions received	125% of prior three-year average	Excess distribution
2020	£1,600	First year of holding	None
2021	£400	£2,000	None
2022	£11,000	£1,250	£9,750
2023	£37,000	£5,417	£31,583
2024	£41,000	£20,167	£20,833
2025	£34,000	£37,083	None

The excess portion in 2022, 2023 and 2024 is not simply taxed as income of that year. It is allocated day by day across the holding period. The slice allocated to the current year is ordinary income. The slices allocated to earlier years are taxed at the highest individual rate in force for each of those years, and an interest charge runs from each year's original due date. The non-excess portion is an ordinary dividend, which does not qualify for the lower qualified dividend rates because the payer is a PFIC.

Two refinements matter in practice. The computation is made share by share, so units bought by the sweep at different dates each have their own holding period and their own three-year history. And a client who added substantially to the fund part-way through sees the newer units treated under the first-year rule while the older units generate excess distributions. On an account where the sweep traded weekly, this is a substantial data exercise.

Excess distribution: accumulating classes and redemptions

An accumulating class pays nothing out, so there is no US income until units are redeemed. At that point the whole gain, which is in substance several years of rolled-up interest, is treated as an excess distribution and spread back over the holding period with top-rate tax and interest on the earlier-year slices. Because a sweep fund is sold in small parcels throughout the year, there may be dozens of such disposals annually, each matched to its own acquisition lots.

The currency gain nobody expects

US tax is computed in dollars. A stable-value fund bought at one pound and redeemed at one pound has no sterling gain, but if sterling strengthened against the dollar between purchase and redemption, there is a dollar gain on PFIC stock, and it falls within the excess distribution rules. If sterling weakened, the loss is outside those rules and is dealt with under the ordinary loss provisions. On large balances held through a volatile exchange-rate period, this currency component can exceed the interest itself.

Mark-to-market: is a liquidity fund marketable stock?

The mark-to-market election is available only for marketable stock. An open-ended foreign fund that is not exchange-traded can qualify if it is comparable to a US regulated investment company and meets a set of regulatory conditions: broadly, at least one hundred unrelated shareholders, shares readily available to the general public at net asset value, a minimum initial investment of no more than $10,000, net asset value published at least weekly, annual audited financial statements, and supervision by a foreign regulator.

Retail share classes of sterling money market funds usually satisfy these conditions. Institutional liquidity classes are a different matter: many carry minimum initial investments in the hundreds of thousands or millions of pounds, and are offered only through professional intermediaries. Whether such a class is marketable stock needs to be checked against the fund's prospectus, class by class, before an election is relied upon. This is a point that generalist commentary on PFICs does not address.

Where the election is available, the result for a stable-value distributing class is unusual. The distributions are ordinary income, and the year-end mark is purely an exchange-rate adjustment. In a year when sterling rises, the taxpayer reports ordinary income on a fund that did not move in sterling terms. In a year when it falls, the loss is deductible only up to the mark-to-market income previously included for that fund. The election cannot be made retroactively for missed years, and in the first year it applies to stock previously held under the default regime, the opening mark-to-market gain is itself taxed under the excess distribution rules.

QEF: the right answer that is rarely available

A QEF election taxes the shareholder each year on a share of the fund's ordinary earnings, which for a cash fund is simply its net interest. That closely mirrors how HMRC taxes the same holding and removes the interest charge entirely. It requires the fund to issue a PFIC Annual Information Statement each year. Few sterling money market funds do, and a late election for past years is permitted only in narrow circumstances. Where a statement is available, it is worth obtaining for the future.

How does HMRC tax the same fund?

As a UK resident you are taxed on the fund's income in the UK as well, and the UK characterisation is different from the US one.

• Interest, not dividends. A fund holding more than 60% of its assets in interest-bearing investments pays interest distributions. For an individual these are savings income, taxed at income tax rates, eligible for the Personal Savings Allowance and, where relevant, the starting rate for savings. HMRC's guidance on tax on savings interest confirms that interest distributions from authorised funds count as savings income. An additional-rate taxpayer has no Personal Savings Allowance.
• Paid gross. Interest distributions from UK authorised funds have been paid without deduction of tax since April 2017, so the tax is collected through Self Assessment.
• Accumulation classes are taxed annually. The income retained in an accumulation class is taxable each year as if it had been distributed, and is added to the capital gains base cost of the units.
• Offshore funds. Many sterling liquidity funds are domiciled in Ireland or Luxembourg. If the fund is on HMRC's list of reporting funds, the investor is taxed each year on distributions and on any excess reportable income, again as interest where the 60% test is met. If it is not a reporting fund, a gain on disposal is taxed as income as an offshore income gain.
• Inside an ISA. The income is free of UK tax. The US does not recognise the wrapper, so the fund remains a fully taxable PFIC on the US return, with no UK tax to credit.

US and UK treatment compared

Issue	US / IRS	UK / HMRC
Nature of the holding	Shares in a PFIC	Units or shares in an authorised or offshore fund
Character of distributions	Non-qualified dividend; excess portion taxed under section 1291	Interest (savings income)
Accumulating class	No income until redemption under the default regime; annual inclusion under QEF or mark-to-market	Taxed annually on income retained or excess reportable income
Redemption	Dollar gain, including currency gain, taxed as an excess distribution	Capital gain computed in sterling, usually negligible for a cash fund
Tax year	Calendar year	6 April to 5 April
Annual allowance	None specific to the fund	Personal Savings Allowance, if available
Reporting	Form 8621 per fund, plus FBAR and Form 8938 for the account	Self Assessment, interest pages or foreign pages

Foreign tax credits: where the mismatch bites

UK income tax paid on the fund's income is generally creditable in the US in the passive category. For a distributing class the credit works reasonably well on the non-excess portion: the UK rate on savings income for a higher or additional-rate taxpayer is typically above the US rate on the same income. Three frictions remain.

• Timing on accumulating classes. HMRC taxes the income every year. Under the default regime the US taxes nothing until redemption. The UK tax is paid in years when there is no matching US income from the fund, and the credit must be carried to a year in which it can be used.
• The interest charge. Foreign tax credits can reduce the deferred tax on an excess distribution within limits, but they do not reduce the interest charge.
• Net Investment Income Tax. PFIC income of higher earners is generally within the 3.8% Net Investment Income Tax, which foreign tax credits do not ordinarily offset.

The US-UK treaty does not disapply the PFIC rules for a US citizen: the saving clause preserves the right of the United States to tax its citizens as if the treaty were not in force.

How does this overlap with the FBAR and Form 8938?

Form 8621 reports the fund. The FBAR and Form 8938 report the account. All three can be required for the same holding.

• FBAR (FinCEN Form 114). The platform or portfolio account is a foreign financial account. It is reported, at its maximum value for the year, if the aggregate of all non-US accounts exceeded $10,000 at any time. A cash fund held directly with the fund operator is itself a reportable account. Our FBAR penalty calculator illustrates the exposure for missed years.
• Form 8938. For a taxpayer living abroad, the filing thresholds are $200,000 at year end or $300,000 at any time for a single filer, and $400,000 or $600,000 on a joint return. The account is reported on the form. A PFIC already reported on Form 8621 need not be itemised again; instead the number of Forms 8621 filed is noted on Form 8938. The value of the fund still counts towards the threshold.

A common pattern in the files we review is an account that was correctly reported on the FBAR and Form 8938 for years, with the cash fund inside it never reported on Form 8621. The account-level disclosure is helpful evidence of good faith, but it does not replace the missing form.

What are the consequences of the missed years?

There is no fixed monetary penalty attached specifically to a late Form 8621. The consequences are indirect but significant:

• An open assessment period. Where a required Form 8621 is omitted, the period in which the IRS may assess tax for that year can remain open until the form is filed. Where there is reasonable cause, the extension is limited to the items related to the omission.
• Misreported income. Distributions are often reported as bank interest, which understates tax where part was an excess distribution, or omitted altogether for accumulating classes and ISA holdings.
• Accuracy penalties and interest on any resulting underpayment, outside a recognised disclosure route.
• Related failures. Missed FBARs and Forms 8938 carry their own, much heavier, penalty regimes.

For most cash-fund cases the additional US tax is modest relative to the balance, because the income is small as a percentage and UK tax credits absorb much of it. The value of regularising lies in closing the assessment period and removing the exposure on the related account-level forms.

How are unreported years put right in a catch-up filing?

Streamlined Foreign Offshore Procedures

Where the omission was non-wilful, a UK-resident American who meets the non-residency test, broadly at least 330 full days outside the United States in at least one of the last three years with no US abode, can use the IRS Streamlined Filing Compliance Procedures. The submission comprises:

• the most recent three years of original or amended federal returns, with every required Form 8621 and Form 8938;
• the most recent six years of FBARs;
• payment of the tax and interest shown as due; and
• a certification on Form 14653 that the failure was non-wilful, with a specific factual narrative.

No miscellaneous offshore penalty applies under the foreign offshore route. Our streamlined filing team prepares these submissions for clients with multi-account portfolios. Where the returns were otherwise complete and no additional tax arises, amended returns or the delinquent information return procedures may be appropriate instead; the choice depends on the facts.

How we prepare the cash-fund computations

1. Identify every cash-like fund. We review each account's holdings and transaction history for money market, liquidity, cash-plus and ultra-short bond funds, including those shown under a cash heading, and confirm the legal form, domicile and share class of each.
2. Rebuild the unit history. Every sweep purchase and redemption is listed with dates, units and sterling amounts back to the first acquisition, because the excess distribution computation depends on the full holding period even though only three years of returns are filed.
3. Translate into dollars. Purchases, distributions and redemptions are converted at appropriate exchange rates so that currency gains and losses are captured.
4. Run the distribution test by year and by lot. We apply the 125% test, allocate any excess across the holding period, and compute the deferred tax and interest charge.
5. Compute redemption gains for accumulating classes and for currency movement on stable-value classes.
6. Match UK tax. Self Assessment figures are mapped onto US calendar years and credited on Form 1116 to the extent the rules permit.
7. Prepare Form 8621 for each fund and year, and reconcile the account values to the FBAR and Form 8938.

Dealing with the holding going forward

The catch-up filing is also the point at which the future treatment is settled on the return. If a mark-to-market election is available for the share class, making it stops further deferral; for a stable-value fund the opening gain subject to the excess distribution rules is normally limited to currency movement. Where the fund has simply been redeemed and the cash moved to deposits, the final Form 8621 reports that redemption. The reporting consequences of each route are different, and we set them out with figures before the returns are filed.

Check the UK side at the same time

The same review frequently finds UK omissions: interest distributions above the Personal Savings Allowance not declared, accumulation income overlooked because no cash was paid, or excess reportable income from an offshore liquidity fund never reported. Our UK tax services team corrects the HMRC position within the same engagement, so the sterling and dollar figures reconcile and the foreign tax credits claimed in the US are supported by UK tax actually paid.

What records should you gather?

• Platform transaction histories for every account, including cash and sweep ledgers, from the date the account was opened.
• Annual consolidated tax certificates and income statements.
• The full legal name, identifier, domicile and share class of each cash fund, and its prospectus or key information document for minimum investment terms.
• Any PFIC Annual Information Statement the fund publishes.
• UK Self Assessment returns and calculations for the corresponding years.
• US returns, FBARs and Forms 8938 already filed.

Why cash funds need a specialist cross-border preparer

A cash fund is technically the simplest PFIC and practically one of the most laborious. The tax at stake is usually small, the number of transactions is large, and the answer depends on details that generalist preparers seldom check: the share class, the minimum investment, the exchange rate on each sweep and the UK character of each receipt. Preparers who are unfamiliar with UK platforms report the fund as a bank balance. Preparers unfamiliar with UK tax miss the credit. Our US-UK tax accountants prepare both sides for high-net-worth clients, so that the US return, the UK return and the information forms tell the same story.

If your UK portfolio holds, or has held, a sterling money market or liquidity fund and Form 8621 was never filed, the position can be corrected in an orderly way and, in most non-wilful cases, without penalty. Jungle Tax will review your statements, identify each fund and year affected, and prepare the complete catch-up filing. To arrange a confidential consultation, contact our cross-border team.