HMRC Offshore Funds Letter Form 8621 Fixes for US Investors

If HMRC's offshore funds letter has reached a UK-resident American, the fund list it prompts you to check is almost always a list of PFICs too. Where the UK return needs correcting for a non-reporting fund or unreported excess reportable income, the US side usually needs years of missing Form 8621 filings as well. Fix both from one reconciled inventory.

That is the short version. The rest of this guide sets out how an offshore funds letter Form 8621 correction works in practice for a US citizen or green card holder living in Britain: what the HMRC letter actually asks, how to build a two-sided inventory of every fund, share class and year, why the UK and US corrections are separate calculations, and how to sequence a UK amendment or disclosure alongside a US Streamlined Foreign Offshore filing. It is written for investors with substantial, multi-fund portfolios held through UK and offshore custodians, where the numbers justify getting the order of work right.

What is the HMRC offshore funds letter?

It is a one-to-many letter HMRC began sending in autumn 2026 to people who hold, or recently held, offshore funds. HMRC frames it as an educational campaign and states it is not a compliance check. It asks you to confirm that your Self Assessment returns include all income and gains from those funds, and to correct them if not.

The practical point in the letter is that a fund's UK tax treatment depends on whether it held reporting fund status, and that status can differ between sub-funds, share classes and periods. Two share classes of the same sub-fund, one distributing in sterling and one accumulating in dollars, can sit on opposite sides of the line. The letter points investors towards the fund manager's investor reports and HMRC's published list of approved offshore reporting funds, which is updated monthly and can be searched by ISIN.

What the letter is not

• It is not an enquiry. On HMRC's own description it is educational rather than a formal compliance check. That does not make it safe to ignore: a letter tells you HMRC believes you hold, or held, offshore funds, and any later enquiry starts from that footing.
• It is not a fund-by-fund verdict. HMRC does not tell you which of your holdings were reporting or non-reporting. You have to establish that yourself, by share class and by period.
• It says nothing about your US position. The letter is a UK document about UK returns. It does not mention PFICs, Form 8621 or the IRS, and nothing here suggests HMRC passes fund-level data to the US. The US exposure exists because of your citizenship, not because of the letter.

We deliberately do not quote any response date from the campaign. If your letter gives one, work to it; if it does not, treat the matter as current rather than optional, because the time limits that govern UK corrections keep running whatever the letter says.

Why does an HMRC fund letter matter to an American investor?

Because nearly every non-US pooled fund the letter covers is also a passive foreign investment company for US purposes. A US person holding one must generally file Form 8621 for it each year. UK-resident Americans who never knew this often have several years of missing 8621s, which the same fund records will now expose.

The overlap is close to total. HMRC's offshore funds rules catch non-UK collective investment schemes: Irish and Luxembourg UCITS, Channel Islands funds, offshore ETFs and similar vehicles. The US PFIC definition catches any non-US corporation that meets either a passive income test or a passive asset test, and a fund taxed as a corporation for US purposes will meet one almost by design. So the list of holdings you assemble to answer HMRC is, line for line, the list of PFICs your US return should have been reporting.

There is one structural difference worth stating early. HMRC's question is about tax: did you declare the right income and gains? The IRS question is partly about information: even in a year with no sale and no distribution, Form 8621 can still be required. The IRS page for Form 8621 describes the annual filing obligation, and the instructions set out a limited de minimis exception that falls away in any year with a distribution or disposal that triggers section 1291. For a high-value portfolio that exception rarely helps.

If the funds sit inside a stocks and shares ISA, the UK side is simpler, since HMRC's helpsheet confirms ISA fund income and gains do not need declaring, but the US side is not. That situation has its own guide: unreported ISA funds and the Form 8621 Streamlined pack.

How do you build a two-sided fund inventory?

List every non-US fund holding by ISIN and share class, then record for each UK tax year whether that class held reporting fund status, and for each US tax year whether it was a PFIC, whether any annual information statement existed, and what happened: purchase, distribution, sale, switch or nothing.

This is the single most useful document in the whole exercise. HMRC wants one view of it, the IRS another, and most errors we see come from building the UK schedule and the US schedule separately and then finding they disagree on cost, dates or units. Build it once, in one place, with one row per share class per year.

The columns that matter

Two calendars sit underneath this table. The UK tax year runs from 6 April to 5 April; the US year is the calendar year. A disposal on 20 February 2025 falls in UK 2024-25 and US 2025. Excess reportable income is treated as arising on the fund distribution date, six months after the fund's reporting period ends, which can push it into a different year again. The interplay between those dates is covered in our guide to excess reportable income and the US year mismatch.

Checking reporting status properly

Do not rely on the fund's marketing name. Open HMRC's published list, search by ISIN, and check the period of approval against the dates you held the class. Where a class entered or left the regime part way through your holding, note the exact dates, because the UK computation may need to split. Where the list is silent, ask the fund administrator for written confirmation and keep it with the file. Never infer a share class's status from a sister class.

Why are there two separate corrections, not one?

Because the UK and US tax the same fund under unrelated rules. A non-reporting fund disposal produces a UK offshore income gain taxed as income. The same sale, for a US person without an election, produces a section 1291 excess distribution spread back over the holding period with an interest charge. Different bases, different years, different currencies.

On the UK side, HMRC's HS265 helpsheet on offshore funds explains that a gain on disposing of a non-reporting fund is normally an offshore income gain, charged to income tax rather than capital gains tax and reported on the foreign pages. For an additional rate taxpayer that means the top income tax rate instead of the capital gains rate, with no annual exempt amount to absorb it. The UK mechanics, including why US-domiciled funds are themselves non-reporting in British hands, are in our guide to non-reporting funds and offshore income gains.

On the US side, a PFIC with no QEF or mark-to-market election in place is a section 1291 fund. The whole gain on sale is an excess distribution. It is allocated rateably across each day of the holding period. The slice falling in the year of sale, and any slice before the fund was a PFIC in your hands, is ordinary income. Each earlier year's slice is taxed at the highest individual rate for that year, and an interest charge runs from that year to the year of sale. Large distributions are treated the same way to the extent they exceed 125% of the average of the previous three years.

Why neither credits cleanly against the other

The instinctive answer is that UK tax paid on the offshore income gain should simply offset US tax on the same sale. In principle, foreign tax on an excess distribution can be taken into account; section 1291 contains its own foreign tax credit rules. In practice the match is rarely clean, for reasons that each need checking on the facts:

• Different years. UK tax falls in one UK tax year; the US tax is split between the year of sale and a deferred tax amount attributed to earlier years.
• Different amounts. The UK gain is computed in sterling; the US gain in dollars on historic exchange rates. Currency movement alone can make the two gains differ materially.
• The interest charge. The US interest on deferred tax is not a tax, and UK tax does not reduce it in the way investors expect.
• Treaty mechanics. The US-UK treaty's savings clause preserves US taxation of its citizens, and how relief interacts with the 1291 regime is a technical question rather than a given.
• Excess reportable income. UK tax already paid on reportable income in earlier years does not create a matching US income inclusion, so there is often no US tax for that UK tax to sit against in the same year.

We treat the credit position as a calculation to be proved for each disposal, not an assumption, and every computation of this kind should be reviewed by the firm before filing. What can be said safely is that correcting one side does not correct the other, and a UK payment does not remove the need for the missing 8621s.

Which comes first, the UK correction or the US Streamlined filing?

Usually the inventory first, then the UK figures, then the US pack. The UK route decides the sterling numbers and the year each gain belongs to, and those feed the US computation. Both filings should tell the same factual story about how the omission happened, because a careless UK narrative and a non-willful US certification must be consistent.

The UK route

Where the year is still open for amendment, you amend the Self Assessment return; HMRC's guidance on correcting a return sets out when that window closes. For older years, the route is a voluntary disclosure, which for offshore matters is normally made through HMRC's digital disclosure process. HMRC's assessment time limits for offshore income and gains are longer than for onshore matters, which is one reason the letter reaches back several years. The behaviour you describe in a UK disclosure, whether reasonable care, careless or deliberate, drives penalty exposure, so it must be considered with care rather than ticked.

The US route

For an American who has lived outside the US throughout, the Streamlined Foreign Offshore Procedures are the usual vehicle for a non-willful catch-up. They require the most recent three years of returns, with all required information returns including Form 8621, the most recent six years of FBARs, payment of tax and interest, and a signed Form 14653 certification. Eligibility turns on the non-residency test and on the failure being non-willful.

Two points specific to PFICs. First, although Streamlined covers three return years, a sale in one of those years still requires the full holding period history to allocate the gain, so records may be needed from well before the Streamlined window. Second, failure to file Form 8621 can keep the statute of limitations open for the relevant return, which is one reason to file the missing forms properly rather than leave them out. Our Streamlined filing team builds the 8621s from the same inventory used for the UK work.

A sequencing plan

1. Stop and preserve. Keep the HMRC letter, note the date received, and avoid any new switches or sales in the affected funds until the inventory is done, so the facts stop moving.
2. Collect the records listed in the next section for every fund held at any time in the review period.
3. Build the two-sided inventory by ISIN, share class and year, confirming reporting status against HMRC's list.
4. Quantify the UK position year by year: excess reportable income omitted, distributions omitted, offshore income gains wrongly treated as capital gains or not declared.
5. Choose the UK route for each year: amendment where still open, disclosure for older years, with a consistent account of how the error arose.
6. Quantify the US position: which PFICs required 8621 in each of the three Streamlined years, any excess distributions and 1291 computations, and the foreign tax credit analysis.
7. Check FBAR and Form 8938 coverage for the accounts holding these funds across the six-year FBAR window.
8. Reconcile before filing. Cost, units, dates and proceeds must agree across the UK disclosure and the US pack, allowing only for currency and calendar differences you can explain.
9. File and pay on both sides, then keep the reconciliation workpaper with both submissions.
10. Set up ongoing compliance so each future year's ERI, OIGs and Form 8621s are handled from the same schedule.

What records do you need to collect?

Fund investor reports for each reporting period, showing excess reportable income per unit; contract notes for every purchase, sale and switch; annual custody statements; distribution records; corporate action notices such as mergers or share class conversions; and written confirmation of reporting status where HMRC's list is unclear.

• Investor reports. Reporting funds must make their reports available to investors each period. These are the source of the ERI figure per unit, and of the fund distribution date that fixes the UK tax year.
• Acquisition records. Trade date, units, price and currency for every lot. Regular savings plans and dividend reinvestment create many small lots, each with its own US holding period.
• Disposal records. Including switches between share classes, which can be disposals for one or both systems. A switch from a non-reporting to a reporting class of the same sub-fund needs particular care in the UK.
• Distribution history. At least three prior years for any fund where the 125% excess distribution test is in point.
• Exchange rates. Dates and sources used for every sterling to dollar conversion, applied consistently.
• Any annual information statement or PFIC statement the fund has ever issued, even if no election was made; its absence should also be recorded.
• Prior returns on both sides, so you can show exactly what was and was not declared.

Where a custodian cannot reproduce historic contract notes, reconstruction from statements is possible but must be documented, and the method used on the UK side should be the method used on the US side.

Worked example: three funds over five years

The following is an illustration with figures we have chosen, not a real client. Assume an American citizen, resident in the UK throughout and an additional rate taxpayer, who received the HMRC letter in autumn 2026. Between April 2021 and April 2026 she held three non-US funds through a UK custody account, and has never filed Form 8621.

Fund B in numbers

UK side: £180,000 of offshore income gain at the additional rate is roughly £81,000 of income tax, against the capital gains tax she originally paid on the same gain, plus late payment interest and any penalty arising from the disclosure. The gain falls in UK tax year 2024-25.

US side: assume a dollar cost of about $500,000 and dollar proceeds of about $754,000, so a gain of roughly $254,000. The holding period is about 1,950 days, of which about 290 fall in 2024. Allocated rateably, roughly $37,500 is ordinary income in 2024 and roughly $216,500 is spread across 2019 to 2023. Each of those earlier slices carries tax at the top rate for its year plus an interest charge running to 2024. On these assumptions the deferred tax alone is in the region of $80,000 before interest and before any foreign tax credit.

What this shows is not the final bill, which depends on the credit analysis and her other income, but the shape of the problem: a single sale produces a UK correction in 2024-25 and a US computation reaching back five calendar years, in a different currency, with no automatic link between them. Fund A shows the reverse: a meaningful UK correction for ERI and a US correction that is largely about missing forms rather than tax. Fund C shows that a holding with nothing to fix in the UK can still be a gap in the US pack.

What do the UK and US positions look like side by side?

The two systems ask different questions of the same holding. HMRC cares about reporting status and income character; the IRS cares about PFIC status and whether an election ever existed. A summary comparison helps clients see why one correction never closes the other.

What mistakes come up most often?

• Answering HMRC and forgetting the IRS. A UK-only disclosure leaves the 8621 gap untouched and creates a documented record of fund holdings the US returns never mentioned.
• Using the wrong share class. Checking the reporting status of the sterling class when you held the dollar class is the most common error in this area.
• Assuming a reporting fund fixes the US position. UK reporting status has no bearing on PFIC classification. Fund A in the example is still a section 1291 fund.
• Mismatched cost figures. Different base costs on each side invite questions from both authorities.
• Treating the letter as a deadline-free reminder. HMRC's time limits and interest run regardless, and voluntary correction is generally treated more favourably than correction after an enquiry opens.
• Recent arrivals overlooking pre-2025 years. Someone previously taxed on the remittance basis may have had a different UK answer for earlier years than for years after the regime changed in April 2025; each year needs checking on its own basis.

How Jungle Tax handles this work

Jungle Tax prepares both sides of this correction from one inventory: the UK amendment or disclosure through our UK tax services team, and the US Streamlined pack with every missing Form 8621 through our IRS compliance team. We do not advise on which funds to hold. Our role is to establish what you held, how each system treats it, and to file returns that agree with each other. For clients with larger or more complex portfolios, our high-net-worth service coordinates the custodian requests and record reconstruction, and the FBAR penalty calculator gives an early sense of the FBAR side before the full review.

If you have received HMRC's offshore funds letter and you are a US citizen or green card holder, the safest first step is a confidential review of your fund list before you reply to anyone. Contact our cross-border team to arrange a discreet consultation, and we will tell you, fund by fund and year by year, what needs correcting on each side of the Atlantic.