US-UK Tax
US-UK tax, joined up on both sides
If you are an American living in the UK or a Brit living in the US, you are inside both countries’ tax nets at once. The treaty and foreign tax credits exist to stop you paying full tax twice; the difficulty is in the detail.
The Short Answer
Americans living in the UK are taxed by both countries: the US taxes its citizens and green-card holders on worldwide income wherever they live, while the UK taxes you on your UK income and, once you are UK resident, generally your worldwide income too. You file in both places, but the US-UK treaty and foreign tax credits stop most income being taxed twice.
The difficulty is in the detail, where the two systems define income, gains, pensions and timing differently. Getting the interaction right is what keeps your total bill fair rather than doubled.
We coordinate the UK side of your affairs, working alongside your US preparer, on fixed fees agreed upfront.
What We Do
Handled for you, end to end
- UK Self Assessment returns for Americans in the UK, coordinated with your US preparer
- US-UK treaty claims and Foreign Tax Credit Relief so the same income is not taxed in full twice
- FBAR and FATCA reporting obligations explained, and the common investment traps such as ISAs and non-US funds
- The 4-year FIG regime applied to US citizens newly resident in the UK
- US LLCs, US retirement accounts and US property held by UK residents
- Residency planning across both systems, including the Substantial Presence Test on the US side
Free In-Depth Guides
Read the guides first, if you like
US-UK Tax
US-UK Tax Guide: Americans in the UK & Brits in the US
Americans in the UK and Brits in the US sit inside two tax nets at once. Getting the interaction right is what keeps the total bill fair rather than doubled.
12 min read · Reviewed June 2026
US-UK Tax
Americans Living in the UK: Tax Explained
How US citizens and green-card holders living in the UK are taxed by both countries, and how to avoid double tax: dual filing, the treaty, FBAR, FATCA, FIG and the big traps.
12 min read · Reviewed June 2026
US-UK Tax
The US-UK Tax Treaty Explained: How It Works for Individuals
How the US-UK double tax treaty works for individuals: the residence tie-breaker, the saving clause, pensions and US Social Security, dividends, interest and Form W-8BEN, explained by a UK Chartered Tax Adviser practice.
13 min read · Reviewed June 2026
US-UK Tax
FBAR and FATCA Explained for UK-Based Americans
A plain-English guide to FBAR (FinCEN Form 114) and FATCA (Form 8938) for US persons in the UK: thresholds, deadlines, penalties, the difference, and how to catch up.
8 min read · Reviewed June 2026
US-UK Tax
UK Tax on a US LLC: The Hybrid Entity Trap
How a UK resident is taxed on a US LLC, the transparent-versus-opaque hybrid mismatch, the Anson case, HMRC's December 2024 practice and the live 2026 reform.
9 min read · Reviewed July 2026
US-UK Tax
401(k), IRA and Roth: UK Tax Treatment
How 401(k)s, traditional IRAs and Roth IRAs are taxed in the UK under the UK-US treaty: periodic payments, lump sums, the 2025 HMRC change, the Roth question and reporting.
8 min read · Reviewed July 2026
US-UK Tax
US Exit Tax: Giving Up a Green Card or Citizenship
A 2026 guide to the US exit tax under section 877A for Brits giving up a green card or US citizenship: covered-expatriate tests, the mark-to-market deemed sale, and pensions.
8 min read · Reviewed July 2026
US-UK Tax
Selling US Property as a UK Resident
A UK resident selling US real estate is taxed in both countries: US FIRPTA withholding plus a US return, and UK CGT on the same gain, with credit relief to avoid double tax.
8 min read · Reviewed July 2026
Country Guides
Moving to the US from the UK: the 2026 tax guide
Become a US tax resident and the United States taxes your worldwide income, not just what you earn in America. This guide walks the UK-to-US move through both systems.
10 min read · Reviewed July 2026
Free Tax Tools
Run your own numbers, before we speak
UK vs US Take-Home Pay Comparator
Free tool: compare your take-home pay in the UK versus the US, including federal, state, National Insurance and FICA, to see the real cost of a transatlantic move. Indicative, 2026.
Try it freeUS Substantial Presence Test Calculator
Free tool: work out whether you meet the US Substantial Presence Test and are a US tax resident, using the 31-day and weighted 183-day three-year day count. 2026.
Try it freeOur Promise
Fixed fees, agreed in advance
We confirm your fee in writing before any work begins. You always know exactly what you are paying, billed as a fixed amount, never in arrears by the hour.
What US-UK work costs
Premium non-resident and expat tax returns are £550, and complex returns covering multiple income streams, investments, trusts, and complex structures are £750+. Advisory and project work is quoted as a fixed fee agreed upfront, scoped to your situation.
See full fixed-fee pricingCommon Questions
Honest answers, before you book
More questions? Read our full FAQ.
Ready When You Are
Start with a free clarity call
Book a free clarity call and we will talk through your situation and confirm a fixed price in writing: no obligation, no pressure, and no surprises.
Prefer email? Reach us at jordanonraet-wells@horizonukts.com