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
Cross-Border Business
Share Options and Equity Awards Across Borders
Taking shares in your employer with a cross-border element? One decision outranks every other: the joint section 431 election, with its hard 14-day deadline from acquisition. This guide covers the election, growth shares and US private equity awards, EMI for mobile employees and US citizens, and how RSUs that straddle a move in or out of the UK are apportioned.
11 min read · Reviewed August 2026
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 July 2026
US-UK Tax
Americans Living in the UK: Tax Explained
Americans living in the UK tax guide: how the US and UK both tax you, dual filing, treaty relief, FBAR and FATCA reporting and the traps to avoid.
12 min read · Reviewed June 2026
US-UK Tax
The US-UK Tax Treaty Explained: How It Works for Individuals
How the US UK tax treaty works for individuals: the residence tie-breaker, the saving clause, pensions, dividends and claiming double tax relief in practice.
13 min read · Reviewed June 2026
US-UK Tax
FBAR and FATCA Explained for UK-Based Americans
FBAR and FATCA explained for Americans in the UK: filing thresholds, deadlines, penalties, key differences and how to catch up safely if you are behind.
8 min read · Reviewed June 2026
US-UK Tax
UK Tax on a US LLC: The Hybrid Entity Trap
US LLC UK tax explained: why HMRC treats an LLC as opaque while the US sees it as transparent, the Anson case, double tax risk and the 2026 reform plans.
9 min read · Reviewed July 2026
US-UK Tax
401(k), IRA and Roth: UK Tax Treatment
401k UK tax rules explained: how the UK-US treaty taxes 401(k) and IRA withdrawals, lump sums, the Roth IRA position and what UK residents must report.
10 min read · Reviewed July 2026
US-UK Tax
US Exit Tax: Giving Up a Green Card or Citizenship
US exit tax explained for 2026: who counts as a covered expatriate, the deemed sale of your assets and what giving up a green card or citizenship costs.
8 min read · Reviewed July 2026
US-UK Tax
Selling US Property as a UK Resident
Selling US property as a UK resident: how FIRPTA withholding, your US return and UK capital gains tax fit together, and how credit relief stops 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.
11 min read · Reviewed July 2026
Moving to the UK
Moving to the UK from the USA: the 2026 tax guide
An American moving to the UK keeps filing US returns for life while picking up UK residence under the SRT. This guide covers arrival timing, split-year treatment, the 4-year FIG regime and the FEIE-to-credit handoff.
9 min read · Reviewed July 2026
US-UK Tax
The PFIC and ISA Traps for Americans in the UK
An ISA is not tax-free for a US citizen, and most UK pooled funds are PFICs with punitive US tax treatment. This guide explains both traps, the mirror-image UK trap for US funds, and how the FIG window changes the picture for new arrivals.
9 min read · Reviewed July 2026
US-UK Tax
The US to UK Arrival Year: How Your First Tax Year Works
Move from the US to the UK mid-year and you sit inside two tax systems at once. This playbook walks through the SRT, the split-year cases for arrivers, claiming the FIG regime on the SA109, the US side in outline and the treaty tie-breaker for the overlap.
8 min read · Reviewed July 2026
US-UK Tax
UK Pensions When You Move to the USA: The Full Picture
Most people moving to the USA simply keep their UK pensions: the treaty protects growth, taxes regular withdrawals only in the US and covers the State Pension too. The 25% tax-free lump sum and the April 2027 inheritance tax change are where the planning lives.
8 min read · Reviewed July 2026
Cross-Border Business
Keeping a UK Limited Company When You Move to the USA
You can keep your UK limited company when you move to America, but the day you become a US tax resident it usually becomes a controlled foreign corporation in the US system. The keep, restructure or close decision is far cheaper to make before that day.
8 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