Introduction
For a high-net-worth individual with a London wealth manager overseeing a multi-asset portfolio that spans UK equities, US securities, alternative investments, and offshore vehicles, the question of tax is rarely straightforward. When that individual is also a US citizen or permanent resident — or when family members hold different nationalities — the tax dimension becomes genuinely complex. A wealth manager can optimize the investment strategy, rebalance the portfolio, and manage custody arrangements with precision. What a wealth manager cannot do is prepare a US federal income tax return, assess passive foreign investment company exposure in the client’s offshore fund holdings, or advise on the interaction between the UK remittance basis and the IRS worldwide income obligation. Specialist US UK tax services that work in direct liaison with the client’s wealth manager fill this gap — and for an HNW individual managing significant cross-border investment income, this coordination is not optional. This guide explains what that coordinated service looks like, why it matters, and what to expect from a first-class advisory engagement. Contact our https://www.jungletax.co.uk/ at Jungle Tax for specialist guidance.
What Are US UK Tax Services?
The Definition
US UK tax services are dual-jurisdiction tax advisory and compliance services delivered by practitioners who hold concurrent expertise in both US federal tax law and UK tax law, and who can manage the full filing and planning picture for clients with obligations to both the IRS and HMRC. For an HNW individual working with a London wealth manager, these services sit alongside — and must be fully integrated with — the investment management relationship. The tax adviser needs to understand the portfolio structure, the income generated by each asset class, the treatment of gains and losses in both jurisdictions, and the reporting obligations that flow from holdings in offshore funds, US securities, and alternative investment vehicles. The IRS overview of tax obligations for US persons with foreign financial interests is published at:
https://www.irs.gov/individuals/international-taxpayers/international-taxpayer-services
Why Wealth Manager Liaison Is a Distinct Service Component
A wealth manager and a tax adviser serve different but overlapping functions for an HNW client. The wealth manager’s primary obligation is to the client’s investment objectives — growth, income, capital preservation, and risk management. The tax adviser’s primary obligation is to ensure that the returns generated by the portfolio are reported correctly in both jurisdictions, that the tax cost of investment decisions is minimized through proper planning, and that compliance obligations — including FBAR, FATCA, Form 8938, and any applicable information returns for offshore fund holdings — are met completely and on time. When these two advisers do not communicate directly, the client bears the cost of the gap between them: investment decisions that generate unexpected tax consequences, gains realized in the wrong tax year, and offshore fund positions that trigger PFIC exposure neither adviser has flagged. Specialist US and ßUK tax services that include direct liaison with the wealth manager eliminate this gap.
Who This Service Is Designed For
This service is intended for US citizens and permanent residents living in the UK who have investment portfolios managed by a wealth manager headquartered in London. It is equally relevant to non-US nationals who have acquired US permanent residency and who hold investment assets managed by a UK firm. It also applies to UK-domiciled or non-UK-domiciled individuals whose portfolios include US securities, US-managed funds, or other US-situs assets that create US reporting obligations even for non-US persons. In each case, the defining characteristic is an investment relationship that generates tax obligations in two jurisdictions simultaneously — and an advisory gap that only integrated US UK tax services can close.
Why US UK Tax Services Matter More Than Ever for HNW Investors in 2026
FATCA Has Made Every Account Visible
Since the Foreign Account Tax Compliance Act came into force, UK wealth managers, custodians, and platform providers are legally required to identify US persons among their client base and report account information — including balances, income, and gains — to HMRC, which passes the data to the IRS under the US-UK Intergovernmental Agreement. A US person whose UK investment portfolio has never been reported to the IRS is therefore not flying under the radar. The account data is already in the IRS system. What is missing is the US tax return that should have accompanied it. Engaging specialist US UK tax services before the IRS raises a query is always less costly than doing so after. The HMRC guidance on FATCA reporting obligations for UK financial institutions is published at:
https://www.gov.uk/guidance/fatca-guidance-notes
The Non-Domicile Reform Changes the Investment Tax Calculus
From April 2025, the UK abolished the remittance basis for individuals who have been UK residents for more than four years, replacing it with a residence-based system. For a non-UK-domiciled US person who had previously sheltered non-remitted foreign income and gains from UK tax, this change removes a significant element of the planning framework. The consequence for the investment portfolio is that foreign-source income and gains — including income from US securities held in custody outside the UK — are now taxable in the UK from the fifth year of UK residence. The interaction of this with the ongoing US worldwide income obligation requires recalibration of both the investment strategy and tax reporting. Specialist US and UK tax services that work directly with the wealth manager can ensure the portfolio structure reflects the new tax reality.
PFIC Exposure in Model Portfolios Is Widely Underestimated
Many London wealth managers construct model portfolios that include offshore collective investment vehicles — UCITS funds, offshore ETFs, and alternative fund structures domiciled in Ireland, Luxembourg, or the Cayman Islands. From a US perspective, these vehicles frequently meet the definition of a passive foreign investment company. A US person who holds an interest in a PFIC without making a timely election is subject to the excess distribution regime. This punishing calculation applies interest charges on deferred gains going back to the year of acquisition. The wealth manager is not responsible for identifying PFIC positions in the portfolio. That responsibility falls on the tax adviser. Without a direct line of communication between the two, the adviser cannot assess the portfolio, and the client bears the cost of the exposure. Our related guidance on accountants for US and UK obligations covers the PFIC rules in detail for investment professionals.
What First-Class US and UK Tax Services Cover for an HNW Investment Portfolio
Investment Income Reporting Across Both Jurisdictions
The foundation of any US-UK tax services engagement for a wealth management client is the correct reporting of investment income — dividends, interest, rental income from REITs, and gains from securities sales — in both the UK and US tax returns. In the UK, investment income is reported on self-assessment, with the applicable rate depending on the taxpayer’s residence, domicile, and the type of income. In the United States, the same income is reported on Form 1040, with different rates applying to different income categories: qualified dividends at preferential rates, ordinary dividends at marginal rates, short-term gains at marginal rates, and long-term gains at the applicable capital gains rate. The foreign tax credit mechanism allows UK tax paid on the same income to offset the US liability — but only up to the proportion of total US tax attributable to that income, and only within the correct income basket under IRC Section 904. Getting this calculation right requires the tax adviser to have full visibility of the portfolio’s income and gain composition for each tax year.
PFIC Assessment and Election Management
Every offshore fund position in the portfolio must be assessed for PFIC status at the point of acquisition and reviewed annually thereafter. Where a PFIC is identified, the adviser must make a timely election — typically the mark-to-market election for liquid positions — to avoid the default excess distribution regime. The mark-to-market election requires the adviser to obtain the fund’s year-end net asset value for each year the election is in force, which, in turn, requires direct communication with the wealth manager or the fund administrator. This is precisely the kind of coordination that a siloed advisory arrangement cannot deliver. The IRS Form 8621 instructions set out the election options and their consequences at:
https://www.irs.gov/instructions/i8621
FBAR and FATCA Reporting for Investment Accounts
Every investment account held by a US person at a UK wealth manager or custodian is a potential FBAR-reportable account. The FBAR filing threshold is an aggregate balance of $10,000 at any point during the calendar year across all foreign financial accounts — a threshold that most HNW investment portfolios exceed in a single account. Separately, Form 8938 must be filed where the aggregate value of specified foreign financial assets exceeds the applicable threshold: $200,000 on the last day of the year, or $300,000 at any point during the year, for single filers living outside the United States. Both filings require the highest annual balance for each account — information that must be obtained from the wealth manager or custodian and incorporated into the tax return preparation process. A specialist adviser who liaises directly with the wealth manager can obtain this data efficiently and accurately.
How Specialist US UK Tax Services Are Delivered for a Wealth Management Client
The delivery of integrated US-UK tax services for an HNW wealth management client follows a structured annual cycle, with key touchpoints aligned to the UK and US filing calendars.
Step one — Onboarding and portfolio review.
At the outset of the engagement, the adviser conducts a full review of the investment portfolio — every holding, every account, every offshore fund position — to identify PFIC exposure, establish the FBAR and FATCA reporting scope, and understand the income and gain composition across all asset classes. A direct introduction to the wealth manager is established to facilitate ongoing data sharing.
Step two — Annual data collection from the wealth manager.
At the close of each tax year, the adviser requests a comprehensive data pack from the wealth manager covering: year-end account balances and highest balances during the year for all accounts (FBAR and FATCA); income and gain statements for each holding broken down by income type; year-end NAV for any PFIC holdings subject to the mark-to-market election; and any corporate actions, fund mergers, or restructurings that affect the tax treatment of specific holdings.
Step three — UK self-assessment preparation.
The UK return is prepared using the portfolio income data, with the correct treatment applied to each income category — including the treatment of offshore fund income under the UK offshore fund rules, which can affect whether gains are taxed as income or as capital gains depending on whether the fund is a reporting fund. The HMRC guidance on the UK offshore fund rules is available at:
https://www.gov.uk/hmrc-internal-manuals/investment-funds-manual
Step four — US federal return preparation.
The US return is prepared concurrently, incorporating the same portfolio income data and applying the correct US treatment to each income category. Form 8621 is prepared for each PFIC position. Form 8938 is prepared when the FATCA threshold is met. The foreign tax credit is calculated across the correct income baskets, with the UK tax liability on each category used to offset the corresponding US liability.
Step five — FBAR filing.
FinCEN Form 114 is filed electronically for all reportable foreign financial accounts. The highest balance for each account is reported for the year, drawn from the wealth manager’s data pack. The filing deadline is 15 April, with an automatic extension to 15 October.
Step six — Year-round investment tax planning.
Throughout the year, the adviser provides real-time input on the tax consequences of investment decisions — including the timing of disposals, the tax treatment of corporate actions, and the implications of any proposed changes to the portfolio structure. This advisory input is provided directly to the wealth manager where appropriate, ensuring that investment decisions are made with full awareness of their tax consequences in both jurisdictions.
Step seven — Annual planning review.
At the end of each tax year, the adviser conducts a planning review covering any anticipated legislative changes, the client’s projected tax position for the following year, and any portfolio restructuring opportunities — including the use of ISA wrappers, pension contributions, and loss harvesting — that are available within the constraints of both the UK and US tax systems.
Case Study — A US Citizen with a London Wealth Manager and a PFIC-Heavy Portfolio
Diane is a US citizen who has been a UK resident for seventeen years. Her investment portfolio — managed by a well-regarded London private bank — includes a mix of UK equities, global UCITS funds, an offshore absolute return fund domiciled in the Cayman Islands, and a small allocation to a Guernsey-domiciled property vehicle. The portfolio has a total value of approximately £3.2 million.
Diane had been filing US returns through a New York CPA who received a single consolidated year-end statement from the London bank. The CPA reported the portfolio income correctly as far as the statement allowed — but had never been told about the Cayman fund or the Guernsey vehicle, and had never assessed any of the UCITS funds for PFIC status.
When Diane engaged Jungle Tax, the portfolio review identified the following: the Cayman absolute return fund met the PFIC income test and had never had a Form 8621 filed; two of the UCITS funds in the portfolio also met the PFIC definition based on their asset composition; the Guernsey property vehicle required a separate PFIC or controlled foreign corporation analysis; the offshore UCITS funds were not UK reporting funds, meaning gains were taxable as income in the UK rather than as capital gains — a point the wealth manager had not flagged; and Diane’s FBAR filings for three prior years had understated the highest balance in her main investment account because the CPA had used the year-end balance rather than the intra-year peak.
Jungle Tax established a direct working relationship with the London private bank, obtaining the correct data for FBAR purposes and the year-end NAV figures for the PFIC mark-to-market elections. Amended returns were prepared for three years. Going forward, the adviser provides the wealth manager with an annual pre-year-end briefing on any proposed portfolio changes with implications, including fund switches that could trigger PFIC gain realizations or changes in the offshore fund’s status. The corrected and prospective tax position across the three amended years produced a net saving — after professional fees — of approximately £22,000. Contact our US/UK tax services team at hello@jungletax.co.uk or 0333-8807974 if your situation is similar.
Common Mistakes to Avoid with US-UK Tax Services for Investment Portfolios
Providing the Tax Adviser with Only the Year-End Statement
The most common operational error in a wealth management context is providing the tax adviser with only the annual consolidated portfolio statement, rather than a full transaction-by-transaction report. For FBAR purposes, the highest balance during the year is required — not the year-end balance, which may be lower following year-end withdrawals or distributions. For PFIC mark-to-market purposes, the year-end NAV of each qualifying fund is required. For foreign tax credit purposes, the income must be broken down by type — dividends, interest, gains — and by source country. None of this granularity is available in a year-end summary statement, and a tax adviser who relies solely on this data will produce returns that are technically filed but materially incorrect.
Assuming UCITS Funds Are Not PFICs
UCITS funds — including mainstream equity and bond funds domiciled in Ireland and Luxembourg — are non-US corporations that very commonly meet the PFIC income or asset test. Many US persons living in the UK, and their advisers, assume that because UCITS funds are widely held and regulated, they cannot be PFICs. This assumption is wrong. The PFIC definition applies to any non-US corporation meeting the income or asset test, regardless of how it is regulated or how many investors hold it. A portfolio containing five UCITS funds may have five PFIC positions requiring annual Form 8621 filings. The IRS PFIC guidance is available at:
https://www.irs.gov/instructions/i8621
Not Distinguishing Between UK Reporting and Non-Reporting Offshore Funds
Under the UK offshore fund rules, gains realized on the disposal of units in a non-reporting fund are taxed as income rather than capital gains, at marginal income tax rates rather than at the 20 percent capital gains rate for higher-rate taxpayers. Many wealth managers do not routinely flag the reporting status of offshore funds in their portfolios, and many clients are unaware that the distinction exists. For a US person, a non-reporting fund gain that is taxed as income in the UK falls in a different foreign tax credit basket from a capital gain taxed in the UK, which affects the creditability of the UK tax against the US liability. Getting this wrong results in either an overpayment of US tax or an incorrect claim for a credit.
Failing to Notify the Tax Adviser of Portfolio Changes During the Year
Tax planning for an HNW investment portfolio is not a once-a-year exercise. Fund switches, significant disposals, corporate actions, and changes in the custody structure all have potential tax consequences in one or both jurisdictions. A client who makes a significant portfolio change mid-year without consulting the tax adviser may trigger a PFIC gain realization, a UK income charge on a non-reporting fund disposal, or a change in FBAR reporting requirements — all of which could have been managed differently with advance notice. The wealth manager and the tax adviser should have an established communication protocol that covers material portfolio changes in real time.
How Jungle Tax Can Help — Specialist US UK Tax Services with Wealth Manager Liaison
Jungle Tax is a specialist US-UK cross-border tax advisory firm with deep experience in delivering integrated US-UK tax services for HNW individuals whose investment portfolios are managed by London wealth managers, private banks, and family offices. Our team includes IRS Enrolled Agents and UK-qualified tax practitioners with specific expertise in PFIC assessment and election management, the UK offshore fund rules, FBAR and FATCA compliance for investment accounts, and the foreign tax credit analysis for multi-asset portfolios. We work directly with the client’s wealth manager — establishing a clear data-sharing protocol at the outset of every engagement and providing year-round advisory input on the tax consequences of investment decisions.
Our wealth manager liaison service is not a passive data-collection exercise. We brief the wealth manager on the US tax implications of the portfolio structure, flag PFIC positions that require election management, advise on the timing of disposals to optimize the foreign tax credit position, and provide pre-year-end planning input to enable the wealth manager to make informed decisions before the tax year closes. You can find further information on our US expat tax advisory service page, or read our related guide to US and UK tax advisors for HNW families.
If you are a US person with a UK-managed investment portfolio and you are not confident that the PFIC, FBAR, and foreign tax credit dimensions of your portfolio are being managed correctly, contact our US-UK tax services team at hello@jungletax.co.uk or call 0333-8807974.
Conclusion
For HNW US persons with London-managed investment portfolios, specialist US-UK tax services that work in direct liaison with the wealth manager are the only way to ensure the portfolio’s tax obligations are met correctly in both jurisdictions. The three most important points from this guide are these: UCITS and offshore funds commonly held in London wealth management portfolios frequently meet the PFIC definition and require annual Form 8621 filings; the FBAR highest-balance requirement means year-end statements alone are insufficient data for compliance purposes; and the foreign tax credit analysis for a multi-asset portfolio must be prepared with full visibility of income by type and source, which is only possible through direct co-ordination between the tax adviser and the wealth manager. Closing the gap between these two advisers is the single most impactful step an HNW US person with a UK-managed portfolio can take.
Speak to a Jungle Tax adviser today — contact us at hello@jungletax.co.uk or visit our US-UK tax advisory service page to learn more.
