US UK High Net Worth Tax Services: What Gets Prepared and Filed

US UK high net worth tax services: an introduction

US UK high net worth tax services cover the US and UK returns, and the many information forms, that wealthier families with ties to both countries must file each year. The income itself is often straightforward. However, the reporting around it is not. Funds, companies, trusts and large gifts each bring their own forms and penalties.

This article sets out what gets prepared and filed, and why the two returns must agree. It does not cover investment or planning advice. Our full guide to US-UK tax for founders and executives covers share plans, companies and exits in more depth.

What US UK high net worth tax services cover

The work starts with the US Form 1040 and the UK Self Assessment return. Around them sit account reports, fund reports, company forms, trust returns and gift returns. Each form has its own threshold and deadline. Consequently, the first task is always a full map of what you hold and where.

What high net worth means here

High net worth, in this context, describes people whose assets create extra filing duties rather than any fixed figure. A family with several brokerage accounts, a UK company and a family trust may file a dozen forms. In contrast, someone with a larger but simpler estate may file fewer. Complexity, not size, drives the work.

Why are high-net-worth cross-border returns harder?

They involve more entities, larger sums and two sets of penalties for information that is missing. Each holding must be reported in the right form, in the right currency and in the right tax year. Small errors cost more when balances are larger.

More entities, more forms

A US person who owns or controls foreign companies, partnerships or trusts files information returns for each one. These returns often carry penalties even when no tax is due. Therefore, an unreported holding company or family trust can create exposure on its own. US UK high net worth tax services start by listing every entity.

Timing and currency on larger sums

The US tax year is the calendar year, while the UK tax year runs from 6 April to 5 April. On large disposals, the exchange rate on the day can move the US gain significantly. Meanwhile, the UK computes the same gain in pounds. As a result, a gain in one country can be a smaller gain, or even a loss, in the other.

Two sets of penalties

The IRS and HMRC each penalise late or missing filings under their own rules. On the US side, many information returns carry fixed penalties per form, per year. For example, the IRS describes penalties of up to $10,000 for failing to file Form 8938 in its comparison of Form 8938 and FBAR requirements. Accordingly, missing forms matter as much as the tax.

Which US forms apply to wealthier Americans in the UK?

Most file the FBAR and Form 8938, and many also file fund reports and company or partnership forms. Which ones apply depends on what you hold and how. The list below follows the usual order of work.

FBAR and Form 8938

The FBAR is due if your foreign accounts together exceeded $10,000 at any time in the year. It is filed with FinCEN, as the IRS FBAR page explains. Form 8938 is filed with the tax return. For married couples filing jointly and living abroad, it applies above $400,000 at year end or $600,000 at any time.

Funds and PFIC reporting

A UK unit trust, OEIC or ETF held outside a pension is usually a passive foreign investment company for US purposes. Each one generally needs Form 8621. For larger portfolios, that can mean many forms a year. Our PFIC reporting service prepares these from your platform statements.

Companies and partnerships

US persons with interests in foreign companies may file Form 5471. Similarly, interests in foreign partnerships, including some UK LLPs, can require Form 8865. Foreign disregarded entities and branches can bring Form 8858. From 2026, the income formerly called GILTI is called net CFC tested income, so older guidance needs reading with care.

How are trusts and gifts reported?

Foreign trusts and large foreign gifts are reported on Form 3520, and foreign grantor trusts also file Form 3520-A. UK trusts may need registering with HMRC. US gift tax returns apply to some gifts you make.

Form 3520 for foreign gifts and trusts

Form 3520 reports transactions with foreign trusts and large gifts from foreign persons. The IRS sets a threshold of more than $100,000 in a year for gifts or bequests from a non-resident alien or foreign estate. For gifts from foreign corporations or partnerships, the 2026 threshold is $20,573, according to the IRS page on gifts from a foreign person. The penalty for not reporting is 5% of the gift for each month, up to 25%.

Form 3520-A for foreign grantor trusts

A foreign grantor trust is a non-US trust whose income is taxed to the person who created or funded it. Where a US person is treated as its owner, the trust files Form 3520-A. Some UK family trusts set up by an American fall into this category. Therefore, the trust deed should be reviewed before anything is filed.

UK trust registration

On the UK side, many trusts must be registered with HMRC's Trust Registration Service. HMRC explains who must act in its guidance on how to register a trust as a trustee. Additionally, its overview of trusts and taxes sets out the main charges. US UK high net worth tax services keep both sides of the trust reporting in step.

US gift tax returns

A US citizen who makes gifts above the annual exclusion files Form 709. The exclusion amounts are indexed each year, and gifts to a spouse who is not a US citizen follow separate limits. Furthermore, gifts from a covered expatriate to a US person can trigger a tax on the recipient. We prepare Form 709 from the same records as the UK inheritance tax position.

How does UK inheritance tax affect American families?

From 6 April 2025, UK inheritance tax on worldwide assets depends on long-term UK residence rather than domicile. Many Americans who have lived in Britain for ten years or more are now in scope. A separate US-UK estate tax treaty decides which country taxes first.

The residence-based system from April 2025

You are a long-term UK resident if you were UK resident for at least 10 of the previous 20 tax years. HMRC sets out the test in its guidance on inheritance tax for long-term UK residents. Long-term residents can face UK inheritance tax on non-UK assets. Notably, the status can continue for between three and ten tax years after you leave, depending on how long you lived in the UK.

The nil-rate band and the 40% rate

HMRC's inheritance tax overview gives a threshold of £325,000 and a standard rate of 40% on the part of an estate above it. A reduced 36% rate can apply where 10% or more of the net estate is left to charity. Other reliefs and exemptions also apply. We report the figures; decisions on structuring an estate belong with a solicitor or estate planner.

The US-UK estate tax treaty

The United States and the UK have a separate treaty on estates, gifts and generation-skipping transfers. It decides which country has the first right to tax and how credits work. GOV.UK lists it among the USA tax treaties. Our guide to the US-UK double taxation treaty covers the income tax treaty that sits alongside it.

What records should you keep each year?

Keep statements showing the highest and year-end value of every account, the deeds and accounts of every trust and company, and a written record of every large gift. These records drive the information returns. Without them, the forms cannot be completed accurately.

Account and portfolio statements

The FBAR needs the highest balance of each account during the year. In contrast, Form 8938 and the streamlined penalty base use year-end values. Fund reports need purchase dates, distributions and disposal proceeds. Therefore, ask each platform for a full annual statement, not just a summary page.

Trust deeds and gift letters

The trust deed decides whether a trust is a grantor trust for US purposes and who must report it. Likewise, a short letter recording the date, amount and donor of each large gift makes Form 3520 simple. US UK high net worth tax services depend on these documents more than on any tax figure.

Company accounts and share registers

For each company, keep the annual accounts, the share register and a note of any loans or dividends. These feed Form 5471 and the related US computations. Additionally, they support the UK return where dividends or close company rules apply. Good records keep US UK high net worth tax services efficient year after year.

What does a high-net-worth engagement look like?

It begins with a full map of holdings, moves to one working file for both returns, and ends with every form filed on time. The order matters, because the information returns feed the tax computations. Here is how the work usually runs.

Mapping every holding

We start with a list of every account, fund, company, partnership, trust and property, and who owns each one. Next, we note the country, currency and year-end value of each. That map shows which forms apply. Importantly, it also shows where records are missing before any deadline arrives.

One file for both returns

The US and UK returns are then prepared from the same figures. Gains are worked out in both currencies, and credits are claimed in each direction. As a result, the UK tax shown on the US return matches the UK return. That consistency matters most where balances are large.

An illustrative example

Consider a typical case. Sophie is a US citizen who has lived in London for twelve years with her British husband. She holds a US brokerage account, a UK investment portfolio of funds and a stake in a UK property company. This year, her British parents gave her the equivalent of $250,000.

For Sophie, US UK high net worth tax services would mean an FBAR, Form 8938 and a Form 8621 for each UK fund. The company stake would be tested for Form 5471. The gift from her parents exceeds the $100,000 threshold, so it goes on Form 3520. Finally, her UK return would report her portfolio gains, and the long-term residence position would be noted for inheritance tax.

What we prepare and what we do not

We prepare and file returns and information forms, and we work out the figures in both countries. However, we do not give investment, financial or estate planning advice. Where a decision needs that kind of advice, we work alongside your adviser, solicitor or wealth manager. That keeps the filing accurate and the advice in the right hands.

How US UK Tax Experts can help

We provide US UK high net worth tax services for families with accounts, funds, companies and trusts in both countries. First, we map every holding and list the forms that apply. Next, we prepare the US and UK returns from one file. We then prepare the FBAR, Form 8938, fund reports, company forms and trust and gift returns.

Our FBAR and FATCA service covers account reports, and our PFIC reporting service covers funds. In addition, our treaty relief service covers credits between the two countries. We explain each return before anything is filed.

Conclusion

In summary, US UK high net worth tax services are about reporting more than tax. Funds, companies, trusts and gifts each bring forms with their own thresholds and penalties. Meanwhile, UK inheritance tax now turns on long-term residence. Therefore, a full map of holdings and one file for both returns is the safest way to file.

Contact us

Are you looking for US UK high net worth tax services that keep both returns in step? Email us at hello@usuktaxexperts.com, or describe your holdings through our contact page. We reply within one working day with the forms that apply to you.