Advising Americans in the UK: A Compliance Checklist for Wealth Firms

If your firm advises clients in the UK, some of them are probably American: US citizens, green card holders or dual nationals. They file in both countries, on different tax years, under rules that often point in opposite directions.

Your firm may not prepare these returns, but the data you hold decides how smoothly they go. Here is what to track, who files what, and where your role ends.

Products that work well for a British client can create US tax problems for an American one. An ISA, a UK fund or a pension transfer can each trigger extra US reporting or tax. Spotting that before the product is sold is worth far more to the client than fixing it after.

1. UK: Self Assessment and the FIG regime
   The UK tax year runs from 6 April to 5 April, and online Self Assessment returns are due by 31 January after it ends. Since 6 April 2025, UK residents are taxed on worldwide income and gains unless they claim the four year Foreign Income and Gains regime, which is only open to people who were non-UK resident for the previous 10 tax years. Claiming it costs the personal allowance and the capital gains annual exemption for that year, so it needs modelling. More in our guide to the 2025 UK rules for US expats.
2. US: FBAR (FinCEN Form 114)
   Required when the combined value of accounts outside the US exceeds $10,000 at any point in the calendar year. UK bank, brokerage, ISA and most pension accounts count. Preparers need each account's maximum balance, not just the year end value.
3. US: Form 8938 (FATCA)
   Filed with the US return when foreign financial assets pass the thresholds for filers living abroad: above $200,000 at year end or $300,000 at any time for a single filer, double that for joint filers. See FBAR vs Form 8938.
4. ISAs are not tax-free for the US
   The US does not recognise the ISA wrapper, so income and gains inside it are generally taxable in the US. UK funds held in an ISA are usually PFICs, which adds punitive default tax and usually a Form 8621 for each fund. Check before recommending an ISA to an American client.
5. UK pensions and SIPPs
   The US-UK treaty can defer US tax on pension growth until withdrawal, but how it applies depends on the scheme and the client's facts, and some positions need a treaty disclosure on the US return. Confirm the treatment of each pension with the US preparer, especially before a transfer.
6. Watch for PFICs everywhere
   Most UK and European funds and ETFs are PFICs for a US person. US-domiciled funds avoid the problem but can be hard to buy from the UK. Our PFIC explainer covers the basics.
7. Check US broker access
   US custodians often restrict accounts once a client's address is in the UK, and UK retail access to US funds is limited. The UK's Consumer Composite Investments regime started replacing PRIIPs in April 2026, with the transition running to June 2027, so check what the client can actually buy. If a client has received a letter, use our advisor playbook for restricted accounts.
8. Keep figures for both tax years
   The US taxes the calendar year and the UK taxes April to April. Record income, gains and tax paid by date so each preparer can split them correctly and claim foreign tax credits without gaps.
9. Confirm who files
   Identify the client's US and UK tax advisers and agree when your firm sends them the account data they need.

Checking one client quickly? Our free Expat Client Exposure Check flags custodian, FBAR, Form 8938 and PFIC risk in six questions.

Unless your firm has the right tax expertise, leave preparing and signing these returns to qualified tax professionals in each country. Your role is making sure the financial picture is complete, including accounts held outside your firm, and that product choices do not create US problems the client never saw coming.

Aequify connects a client's accounts across 30+ countries into one view, including assets held elsewhere, and produces tax-ready data packs with FBAR maximum balances and Form 8938 figures for the client's accountant. See how Aequify works for advice firms.

This article provides general information for advisers, not tax or legal advice. Rules and thresholds change, so confirm them with a qualified tax adviser for each client.