Introduction: Why a Discretionary Managed Portfolio Creates US Tax Problems You Never See
A discretionary managed portfolio is how most wealthy families in Britain invest, and it is also the account that most often produces a wrong US tax return. You hand a UK wealth manager authority to buy and sell on your behalf. Consequently, hundreds of decisions with US tax consequences happen every year without anyone asking whether you are an American.
At TaxYork, we prepare US and UK returns for investment bankers, company owners and investors whose portfolios run from £500,000 to well over £20 million. In our experience, the manager's annual tax pack is built for HMRC, not the IRS. Therefore, a return prepared from that pack alone usually misstates gains, omits whole categories of reporting and leaves the tax years open for examination. This guide explains what goes wrong, why it goes wrong and how to fix it.
What a Discretionary Managed Portfolio Actually Is
A discretionary managed portfolio is an investment account in which a regulated manager chooses, buys and sells investments for you within an agreed risk mandate. You do not approve individual trades. Instead, you receive quarterly valuations and a consolidated tax pack after 5 April each year.
By contrast, an advisory portfolio requires your consent before each trade, and an execution-only account leaves every decision to you. The distinction matters because delegation removes your chance to stop a trade that works in Britain but fails in America. For background on how UK managers are authorised, see the Financial Conduct Authority.
Why the Mandate Matters More Than the Returns
Most UK mandates are written for British taxpayers, and a standard discretionary managed portfolio rarely carries any US instructions at all. Accordingly, the manager optimises for UK capital gains tax, ISA allowances and UK reporting funds. None of those priorities line up with the Internal Revenue Code, and some of them actively damage an American's position.
The PFIC Problem Inside a Discretionary Managed Portfolio
The most expensive issue in any discretionary managed portfolio is the passive foreign investment company, or PFIC. Almost every UK-domiciled unit trust, OEIC, investment trust and London-listed ETF is a PFIC for US purposes. Furthermore, a typical UK model portfolio holds between ten and thirty such funds for diversification.
How the Default PFIC Regime Taxes Your Gains
Under section 1291 of the Internal Revenue Code, a gain on selling a PFIC is spread back over your holding period. The amount allocated to earlier years is taxed at the highest ordinary rate for each year, currently 37%, and an interest charge is added. As a result, a gain that would cost 20% plus the 3.8% net investment income tax on an individual share can cost far more inside a fund.
Importantly, the manager of a discretionary managed portfolio rebalances regularly. Therefore, the fund disposals that trigger this regime happen every year, not only when you decide to sell. Investopedia's overview of passive foreign investment companies sets out the basic definitions.
Form 8621 and the Annual Filing Burden
Each PFIC generally needs its own Form 8621. The Form 8621 instructions excuse a holder only where total PFIC value is $25,000 or less, or $50,000 on a joint return, and there is no excess distribution or disposal. Consequently, a discretionary managed portfolio with regular fund trading almost never qualifies for that exception.
In practice, we see portfolios that need fifteen to twenty-five Forms 8621 each year. Moreover, a missing Form 8621 keeps the whole return open to assessment until three years after you file it, so the problem compounds rather than fading with time.
Elections That Soften the Damage
Two elections can replace the default regime. First, the qualified electing fund election requires the fund to supply an annual information statement, which UK funds rarely provide. Second, the mark-to-market election under section 1296 is available for funds regularly traded on a regulated exchange, which covers most London-listed ETFs and investment trusts.
However, mark-to-market taxes the annual increase in value as ordinary income, with no capital gains rate. Accordingly, the best long-term answer is usually a mandate that avoids PFICs altogether, rather than an election that merely manages them.
How UK Tax Rules Inside the Portfolio Collide With US Rules
Even without funds, a discretionary managed portfolio runs on UK rules that the IRS does not recognise. The three collisions we fix most often involve loss harvesting, currency and the tax year itself.
Bed and ISA and the US Wash Sale Rule
UK managers harvest losses by selling a holding and buying it back inside your ISA. HMRC accepts this because the UK 30-day matching rule in its share identification guidance does not reach ISA purchases. By contrast, the US ignores the ISA wrapper entirely.
Under section 1091, a loss is disallowed if you buy substantially identical securities within 30 days before or after the sale. Therefore, a bed-and-ISA transaction that crystallises a useful UK loss usually destroys the US loss. We explain the full interaction in our guide to wash sale rules and UK bed and breakfasting.
Sterling Cash and Section 988
Every discretionary managed portfolio holds sterling cash between trades. For a US citizen, sterling is a foreign currency, so spending it to buy securities can realise an exchange gain or loss under section 988 and its regulations. Additionally, each purchase needs a US dollar cost basis at that day's rate, and each sale needs dollar proceeds at the sale date.
Consequently, a sterling gain in the UK can be a smaller gain, or even a loss, in dollars. We cover the mechanics in detail in our guide to foreign currency gains on GBP accounts.
The Tax Year Mismatch
The UK tax year runs from 6 April to 5 April, while the US year follows the calendar. Therefore, the manager's tax pack for 2024/25 covers nine months of your 2024 US year and three months of 2025. A preparer who copies the UK capital gains summary onto a US return reports the wrong trades in the wrong year.
Instead, you need calendar-year transaction reports, contract notes or a full trade ledger from the custodian. Most managers can produce them, but only if you ask, and many charge for the work.
FBAR, Form 8938 and the Other Reporting on a Discretionary Managed Portfolio
A discretionary managed portfolio held with a UK custodian is a foreign financial account. Accordingly, it belongs on your FBAR and, above the thresholds, on Form 8938. The IRS explains both obligations side by side in its comparison of Form 8938 and FBAR requirements.
Reporting the Maximum Value
For the FBAR, you report the highest balance during the calendar year, converted at the US Treasury rate for the last day of the year, as FinCEN explains in its guidance on reporting foreign bank and financial accounts. For 31 December 2025, the Treasury reporting rate was 0.743 pounds per dollar.
Notably, one discretionary managed portfolio often sits across several accounts: a general investment account, an ISA, a cash account and sometimes a separate currency account. Each has its own account number, so each needs its own FBAR entry.
Form 8938 and the Living Abroad Thresholds
If you live in Britain and file as single, Form 8938 applies once your foreign financial assets exceed $200,000 at year end or $300,000 at any time. For a joint return, the figures are $400,000 and $600,000. Almost any discretionary managed portfolio clears those limits on its own.
Furthermore, the PFICs inside the portfolio are reported on Form 8621 rather than listed again on Form 8938. However, their value still counts towards the Form 8938 threshold. For shares you hold outside the custodian, see our guide to directly held foreign stock and Form 8938.
Why the ISA Offers No US Shelter
Many mandates combine a general account with a stocks and shares ISA. The UK exempts ISA income and gains, but the US taxes them in full and requires the ISA on the FBAR and Form 8938. Consequently, an ISA inside a discretionary managed portfolio is simply another taxable account for your US return, and the funds within it are still PFICs.
Income, Fees and Foreign Tax Credits in a Discretionary Managed Portfolio
The income side of a discretionary managed portfolio looks simple on the UK tax pack. However, each category needs separate US treatment, and the foreign tax credit only works when both returns agree.
Dividends, Interest and Gilts
UK company dividends are generally qualified dividends in the US, taxed at up to 20%. In Britain, from 6 April 2026 the dividend rates are 10.75%, 35.75% and 39.35% above a £500 allowance, as HMRC sets out in its guidance on tax on dividends. Therefore, UK tax usually exceeds US tax, and the foreign tax credit covers the regular federal liability.
Gilts are the exception that surprises clients. Britain exempts gilt gains from capital gains tax, but the US taxes them, often as ordinary income through the market discount rules. We explain why in our guide to UK gilts and US tax.
Management Fees Are Not Deductible
Your manager's fee, often 0.75% to 1.25% a year, reduces your returns but gives you no US deduction. The One Big Beautiful Bill Act made the suspension of miscellaneous itemised deductions under section 67 permanent from 2026. Similarly, HMRC does not allow ongoing management fees against capital gains, although dealing costs and stamp duty form part of the cost.
As a result, a £25,000 annual fee on a discretionary managed portfolio of £2.5 million is a cost you bear from after-tax money in both countries.
Structured Products and Alternative Investments
Many managers add structured notes, hedge fund feeder shares or private market funds to a larger discretionary managed portfolio to diversify returns. Each one raises its own US question. For instance, a capital-protected note may be a contingent payment debt instrument with deemed annual interest, while an offshore feeder fund is almost certainly a PFIC with no marketable share price. Therefore, we ask the manager for the term sheet or offering document before the year end, not after the return is due.
Making the Foreign Tax Credit Work
UK capital gains tax is charged at 18% or 24% after a £3,000 annual exempt amount, according to HMRC's Capital Gains Tax rates. The US taxes long-term gains at up to 20%, plus the 3.8% net investment income tax. Because the Federal Circuit ruled in August 2026 that UK tax cannot be credited against the NIIT under the treaty, that 3.8% is a genuine extra cost.
Moreover, credit timing breaks when gains fall in different years on each side. Our US-UK tax treaty optimisation work aligns both returns so that credits are not stranded.
Building a US-Compliant Discretionary Managed Portfolio
The goal is not to abandon discretionary management. Instead, it is to give your manager a mandate that respects both tax systems, and to give your preparer the data to report it.
What to Ask Your Manager
The instructions you give at the outset shape every trade that follows, so a US-compliant discretionary managed portfolio starts with the investment mandate itself rather than with the tax return. In our experience, managers respond well to precise written instructions and poorly to general requests to "be careful about US tax".
First, confirm in writing that the manager knows you are a US person and will avoid PFICs. Next, ask for direct equities and individual bonds in place of pooled funds, or for fund structures that suit US holders where the manager's permissions allow them. Additionally, ask the manager to stop bed-and-ISA trades and to warn you before year-end loss harvesting.
Some UK firms run dedicated services for US-connected clients through a US-registered adviser. You can check any adviser's US registration on the SEC's Investment Adviser Public Disclosure site. However, a US-aware mandate still produces UK-format tax packs, so you need a preparer who can translate them.
The Records Your Preparer Needs
Your US return for a discretionary managed portfolio needs a calendar-year trade ledger with dates, quantities, sterling amounts and security identifiers. It also needs dividend and interest schedules by payment date, fund-level holdings for every PFIC, and year-end and maximum values for each account. We send a standard data request to managers each January so that the information arrives before the US filing season.
Transitioning an Existing Portfolio
Selling every PFIC in a discretionary managed portfolio at once can trigger a large excess distribution charge in a single year. Therefore, we model the exit over one or two tax years, compare it with a mark-to-market election on the listed funds, and consider UK capital gains tax at the same time. The right sequence depends on the size of each fund's gain and your holding period.
Case Study: A £2.5 Million Mandate and a Return Built From the UK Tax Pack
The following illustrative case study shows how these rules combine. The client and figures are hypothetical, but they reflect the pattern we see most often.
The Facts
Rebecca is an American managing director who has lived in London since 2016. She holds a discretionary managed portfolio of £2,500,000 with a UK wealth manager, split between a general investment account of £2,300,000 and an ISA of £200,000. At the Treasury year-end rate of 0.743, that is $3,364,738. The mandate was standard, and the manager did not know she was American.
During 2025, the manager made 312 trades. At 31 December, the portfolio held 17 UK funds and investment trusts worth £880,000, alongside direct shares, gilts and sterling cash. The fee was 1% a year, or £25,000.
What Her Previous Return Showed
Her previous preparer copied the 2024/25 UK capital gains summary onto her 2025 US return. That reported a net gain of £118,000, converted at the IRS average rate of 0.759 to $155,468, all as long-term capital gain. No Forms 8621 were filed. Furthermore, the ISA and the cash account were missing from Form 8938, although the FBAR listed them correctly.
When we rebuilt 2025 on a calendar-year basis with dollar basis for every lot, the true position was very different. Fund disposals produced $61,000 of PFIC gains taxable under the excess distribution rules. A £40,000 bed-and-ISA loss was disallowed in full under the wash sale rule. Additionally, £190,000 of gilt redemptions produced market discount income that the UK tax pack never showed because the gains were exempt in Britain.
The Fix and the Outcome
Because the errors were non-wilful and she lives abroad, we used the IRS Streamlined Filing Compliance Procedures. We amended 2023, 2024 and 2025, filed 17 Forms 8621 for each year, completed Form 8938 and applied foreign tax credits correctly. The additional federal tax and interest came to about $41,000, with no offshore penalty.
Next, we worked with her manager to convert the mandate to direct holdings over two years and made mark-to-market elections on the listed funds that remained. As a result, her 2026 position needs only four Forms 8621, and her statute of limitations began to run again.
How TaxYork Can Help
TaxYork prepares complete US and UK returns for clients whose wealth sits in a discretionary managed portfolio. Specifically, we request calendar-year data from your manager, rebuild dollar basis lot by lot, identify every PFIC and prepare the Forms 8621, FBAR and Form 8938 that go with it.
Moreover, our US tax returns for expats service reconciles every trade with your UK Self Assessment so that credits line up. Our FBAR and FATCA reporting service covers the account side, and where earlier years are wrong, our IRS Streamlined filing service prepares the corrective filings. For clients who also hold a self-directed account, see our guide to the UK general investment account and US tax.
Conclusion
A discretionary managed portfolio is an efficient way to invest in Britain, but a standard UK mandate is built for HMRC alone. Consequently, PFIC funds, bed-and-ISA trades, sterling cash and the April tax year all create US errors that the manager's tax pack will never reveal.
Therefore, the answer is a US-aware mandate, calendar-year data and a preparer who reconciles both returns. If your US return has been prepared from a UK tax pack, it is worth reviewing now, before the IRS or a future sale forces the question.
Contact Us
If you hold a discretionary managed portfolio with a UK wealth manager, we can review your recent returns and prepare complete US and UK filings. Please book a consultation with our team, email hello@taxyork.com or call 020 3488 8606.
Disclaimer
This article provides general information about US and UK tax rules as they stood in September 2026 and does not constitute tax, legal, investment or financial advice. Outcomes depend on your individual circumstances, and the rules, thresholds and exchange rates described here can change. You should take professional advice on your own position before acting. For professional standards and consumer guidance, see the Chartered Institute of Taxation, the AICPA and CIMA tax resources and MoneyHelper. TaxYork accepts no liability for actions taken on the basis of this article without a formal engagement.