US UK Tax Experts: What Cross-Border Specialists Prepare for You

US UK tax experts: an introduction

US UK tax experts are preparers who work on both the US and the UK tax systems for the same person, so the two returns agree. You need them when you file in both countries, which most Americans in Britain must do. The United States taxes its citizens wherever they live. Meanwhile, HMRC taxes UK residents on their worldwide income.

This article explains who needs cross-border help, what gets prepared each year and how the work runs in practice. Our full guide to US and UK tax returns prepared together sets out how the two returns fit, year by year.

What US UK tax experts actually do

The job is to prepare two returns that describe the same income in two currencies, two tax years and two sets of rules. On the US side, that means Form 1040, foreign tax credits and account reports. On the UK side, it means Self Assessment and any relief for US tax. Above all, it means making the figures on each side match.

What a cross-border tax return is

A cross-border tax return is a return that reports income, accounts or assets connected with another country. For an American in London, both returns are cross-border. The US return reports UK salary, savings and pensions. Similarly, the UK return may report US dividends, rental income or share plan gains.

Who needs US UK tax experts?

You need specialist help if you are a US citizen or green card holder living in the UK, a UK resident with US income or assets, or someone moving between the two countries. In each case, two tax authorities have a claim on the same income. The detail decides which forms apply.

Americans living in Britain

US citizens and green card holders file a US return every year if their worldwide income reaches the filing threshold. The IRS confirms this on its page for US citizens and resident aliens abroad. Most also file UK returns because of savings, rental income or self-employment. Consequently, they need someone who understands how the two returns interact.

US-born British residents

Many people born in the United States left as children and never thought of themselves as American taxpayers. Nevertheless, US citizenship carries a filing duty wherever you live. These people often discover the position when a UK bank asks about US status. In our experience, they need a calm review of what applies before anything is filed.

People moving between the two countries

The year you arrive or leave is usually the hardest. UK residence follows the statutory residence test, which HMRC explains in its guidance on tax on foreign income and residence. On the US side, a move can change state filing duties and the choice between credit and exclusion. Therefore, a move year benefits from planning on both sides at once.

What do US UK tax experts prepare for you?

The core is the US federal return, the FBAR, any Form 8938 and the UK Self Assessment return. Around those sit forms for funds, companies and trusts. Agreeing the scope at the start avoids surprises later.

The US federal return and its credits

Most Americans in Britain claim the foreign tax credit on Form 1116 for UK tax paid. Alternatively, some claim the foreign earned income exclusion on Form 2555. Because UK rates often exceed US rates, the credit frequently works better. However, the right answer depends on your figures, so we model both ways before choosing.

FBAR and Form 8938

The FBAR is a report of foreign financial accounts filed with FinCEN, not the IRS. You file it if your foreign accounts together exceeded $10,000 at any time in the year. Separately, Form 8938 applies to a single filer living abroad above $200,000 at year end or $300,000 at any time. The IRS sets out both tests in its comparison of Form 8938 and FBAR requirements.

The UK Self Assessment return

Self Assessment is HMRC's system for reporting income not fully taxed through PAYE. You may need to register for Self Assessment if you have US income, rental income or untaxed savings. For the 2025 to 2026 tax year, HMRC lists 31 January 2027 for online returns and payment on its Self Assessment deadlines page. Good US UK tax experts prepare this return from the same file as the US one.

Forms for funds, companies and trusts

Several other forms catch Americans in Britain by surprise. A UK fund held outside a pension is usually a passive foreign investment company, which means Form 8621 each year. A US person who controls a UK company may file Form 5471. Additionally, foreign trusts and large foreign gifts can bring Form 3520 into play.

Why prepare both returns from one file?

Both returns report the same income, and each gives credit for tax paid to the other country. If they are prepared separately, the figures rarely agree. One file removes a whole class of mismatch.

Two tax years, one set of figures

The US tax year is the calendar year. In contrast, the UK tax year runs from 6 April to 5 April. Consequently, a single bonus or share sale can fall into different years on each return. US UK tax experts split income between UK years and then map UK tax back to the US year.

Credits that depend on each other

The United States gives credit for UK tax on UK income. Meanwhile, the UK gives credit for US tax on US-source income, within the limits of the treaty. HMRC describes its side in its guidance on income that is taxed twice. Therefore, the credit on one return depends on the final figure from the other.

Currency and timing

Every UK figure on the US return must be shown in dollars. The IRS publishes yearly average currency exchange rates that many preparers use for income. However, some transactions need the rate on the day. Using one consistent method on both sides keeps the credits clean.

How does an engagement with US UK tax experts run?

It starts with a short description of your situation, moves to an agreed scope and a document list, and ends with draft returns you review before filing. The order matters, because the UK figures feed the US return. Here is how the work usually runs.

The first email and the scope

You describe your residence, income, accounts and any gaps in past filing. From that, the preparer lists the forms that apply and the years involved. Importantly, the scope should name every form, so nothing is assumed. A clear scope also shows whether any catch-up work is needed first.

What to send

Send last year's US and UK returns, your P60 or payslips, and statements for every account outside the United States. Add share plan statements, pension statements and details of any property. Finally, note any move between countries, because the arrival or departure year changes the residence position on both sides.

Drafts, review and filing

You should see a draft of each return with a short note on what changed from last year. Furthermore, any judgement call, such as a currency rate or a residence date, should be flagged. Only then are the returns signed and filed. Americans abroad get an automatic extension to 15 June, and Form 4868 extends filing to 15 October, as IRS Publication 54 explains. However, interest runs from 15 April on any unpaid tax.

An illustrative example

Consider a typical case. Michael is a US citizen who moved to Manchester five years ago. He earns a salary taxed through PAYE, holds a stocks and shares ISA and rents out a flat in Ohio. He has filed US returns with an online tool but never filed a UK return or an FBAR.

In this case, US UK tax experts would start with the UK return, because the Ohio rent is taxable in the UK. Next, they would test the ISA funds for PFIC status and file the missing FBARs. Then the US return would claim credit for UK tax on UK income. As a result, Michael ends up with two returns that agree.

What else do cross-border specialists handle?

Beyond the yearly returns, specialists handle the events that change the figures: share awards, pensions, property sales and moves. Each one is taxed under two sets of rules. Consequently, each needs the same joined-up approach as the annual returns.

Share plans from a US employer

Restricted stock units and options from a US parent company are common in London. The two countries can tax the same award at different moments, such as grant, vesting or sale. Therefore, the preparer must track each award and assign the income to the right year on both sides. Otherwise, the credits will not line up.

Pensions on both sides of the Atlantic

UK workplace pensions, US 401(k) plans and IRAs are each treated differently by the other country. The treaty contains specific pension articles, published with the US-UK tax treaty documents. Furthermore, some treaty positions must be disclosed on Form 8833. Our pensions service covers this reporting.

Selling property in either country

A sale of a UK home or a US rental can be taxed in both countries. In addition, HMRC has its own rules for non-residents selling UK residential property. US UK tax experts work out the gain in both currencies and claim credit where the treaty allows. As a result, you avoid paying tax twice on the same gain.

What should you check before hiring US UK tax experts?

Check that the preparer is registered with the IRS, that one person owns the reconciliation between the returns, and that they can handle catch-up filings if needed. These checks take minutes and save problems later.

Preparer registration

Anyone paid to prepare a federal return must hold a Preparer Tax Identification Number. The IRS explains what to look for on its page about choosing a tax professional. Additionally, the preparer should sign the return and give you a copy before it is filed.

Who owns the reconciliation

If two firms prepare the two returns, ask who checks that the UK tax figure on Form 1116 matches the UK return. Without a clear answer, the gap tends to fall on you. Ideally, the same team prepares both or works from the final figures of the other.

How catch-up cases are handled

Many people come to cross-border specialists because they have fallen behind. For non-wilful cases, the usual route is the Streamlined Foreign Offshore Procedures, set out on the IRS page for US taxpayers residing outside the United States. Our guide to IRS Streamlined Filing from the UK explains the steps. Ask how the preparer settles the UK figures for those years first.

How US UK Tax Experts can help

US UK Tax Experts prepares US and UK returns from one file, so the credits on each side agree. First, we review your last returns and list every form that applies. Next, we work out the UK position for the relevant tax years and convert each figure. We then prepare the Form 1040, the FBAR and any information returns, alongside your Self Assessment return.

Our US federal return service covers the Form 1040 and its schedules. Our UK Self Assessment service covers the HMRC side. In addition, our FBAR and FATCA service covers your account reports. We explain each result in plain terms before anything is filed.

Conclusion

In summary, US UK tax experts prepare two returns that describe one life. The work covers the US return and its credits, account reports, fund and company forms, and a UK return that agrees with the US one. Therefore, look for a preparer who owns the reconciliation and sequences the deadlines. Ultimately, the right specialists make two returns behave like one.

Contact us

Are you looking for US UK tax experts to prepare both returns together? Email us at hello@usuktaxexperts.com, or send a short description of your situation through our contact page. We reply within one working day with the filings that apply to you and the dates that matter.