Dual UK-US Tax in 2025
Dual UK-US Tax in 2025 – New IRS and HMRC Changes Every American in Britain Needs to Understand
Living between two tax systems is no small task. For Americans in the UK — whether you’re a permanent resident, dual national, or just here on assignment — navigating dual UK-US tax obligations in 2025 is more complex than ever. Recent updates from both HMRC and the IRS have introduced small but critical shifts in filing expectations, credit claims, and income treatment, which could have major effects on your tax bill if not handled correctly.
At Xerxes Associates LLP, we specialise in helping US citizens, green card holders, and UK-resident dual nationals manage this balancing act. With the UK Spring Budget 2025 introducing changes to capital gains treatment and the US maintaining its global tax policy, many taxpayers are left confused about where to start and how to avoid double taxation.
One of the most common misconceptions among US expats in the UK is that filing taxes in the UK alone is enough. Unfortunately, the US is one of the only countries in the world that taxes its citizens on worldwide income, no matter where they live. This means that even if you pay UK tax on your earnings, dividends, or pensions, you still have to file with the IRS every year — and declare those same income sources.
The good news is that the US-UK tax treaty is designed to prevent double taxation. However, claiming foreign tax credits and the Foreign Earned Income Exclusion (FEIE) requires precision, correct elections, and up-to-date documentation. In 2025, the FEIE threshold has risen slightly due to inflation adjustments, but many Americans in London still earn above the exclusion limit — especially once housing and bonuses are factored in.
Changes to HMRC’s treatment of non-domiciled residents, particularly regarding remittance rules and overseas income, add another layer of complexity. Dual residents who previously enjoyed the remittance basis may now find themselves unexpectedly exposed to UK taxation on foreign income — which then needs to be reconciled on the US side to avoid duplicate payments.
Another emerging issue is how pension contributions and distributions are treated under each tax system. In the UK, certain employer pension contributions and ISAs are tax-advantaged, but in the eyes of the IRS, they may be fully taxable or require detailed reporting on Form 3520 and 3520-A. Mistakes in this area are increasingly flagged during audits.
Cryptocurrency is also on the radar. Both HMRC and the IRS have clarified their stance on digital asset reporting, and new 2025 guidance suggests more aggressive enforcement. If you’ve held or traded crypto while living in the UK, both tax agencies now expect clear, transparent declarations — and inconsistencies between the two filings are increasingly leading to audits.
Perhaps the biggest risk in dual taxation is overlooking one system while focusing on the other. We’ve seen clients pay unnecessary penalties, lose out on tax credits, or miss out on treaty benefits simply because their accountants lacked cross-border expertise. This is where Xerxes Associates LLP makes a tangible difference. We don’t just file forms — we coordinate both your UK and US filings to ensure accuracy, reduce tax liability, and keep you fully compliant across jurisdictions.
Whether you’re a first-time filer, a long-time resident, or someone returning to the UK after years abroad, the dual tax landscape in 2025 demands clarity, strategy, and expertise. With new rules, changing thresholds, and increasing enforcement from both HMRC and the IRS, now is the time to get your international tax affairs in order.
At Xerxes Associates LLP, we help you turn confusion into confidence — and compliance into peace of mind.
Get in Touch
For those seeking guidance on taxation or other expatriate tax matters, Xerxes Associates LLP offers consultations to discuss individual needs and circumstances. To learn more about their services or to schedule a consultation, visit their contact page.
