You're a US citizen living in England. You want to pick up freelance or contractor work from US companies. Great idea — except two tax authorities now want a piece of you. Here's exactly how the US-UK tax treaty, Foreign Tax Credit, and National Insurance rules work together, and how to structure things so you don't pay the same dollar twice.
"US citizen, living in the UK (right to work). Interested in picking up some self-employment work from US companies. I'm finding myself confused about the tax implications... Want to make sure I avoid double taxation, and I do not have the money to pay for a cross-border tax specialist at the moment."
This question comes up constantly, and the confusion is understandable — you're dealing with two of the world's most complex tax systems at once. The good news: there's a clear framework, and once you understand it, you can navigate it without expensive specialists for most situations.
Unlike almost every other country, the US taxes its citizens on global income regardless of where they live. So even if you've been in London for 5 years and all your income comes from UK or US clients, you still file a US return every year. This is non-negotiable.
Meanwhile, the UK taxes you on income earned in the UK and (if you're a UK tax resident) on overseas income too. So on paper, your US contractor income could be taxed by both countries. In practice, there are three mechanisms that prevent this from becoming a disaster:
The Foreign Tax Credit (FTC) is usually your best defense against double taxation as a self-employed US expat in the UK.
Here's how it works: you pay UK income tax first (since you're a UK resident, the UK has primary taxing rights on your self-employment income). Then when you file your US return, you claim a credit for the UK taxes already paid. Since UK income tax rates are typically higher than US rates (UK basic rate = 20%, higher rate = 40–45% vs US rates of 10–37%), the FTC usually eliminates your US income tax liability entirely.
💡 Key rule: The FTC is claimed on IRS Form 1116. You can only claim credits up to the US tax rate on that income — but since UK rates are often higher, this cap usually isn't an issue. Most US expats in the UK end up owing $0 additional to the IRS on self-employment income.
The US-UK tax treaty has been in force since 1980 and provides additional protections. Article 24 specifically deals with relief from double taxation and works alongside the FTC. The treaty is particularly helpful for:
For self-employment income, the treaty generally confirms that the UK (your country of residence) has primary taxing rights — meaning you pay UK tax first and use the FTC to offset US liability.
This is the one that catches people off guard. The FTC covers income tax — but not US self-employment tax (SE tax), which is 15.3% (Social Security + Medicare). Normally, self-employed Americans abroad owe this on top of income tax, and the FTC can't offset it.
However, there's a critical exception for UK residents: under the US-UK Totalization Agreement on Social Security, if you're paying UK National Insurance (NI) as a self-employed person, you are generally exempt from US SE tax on the same income.
💡 What this means in practice: As a self-employed UK resident, you pay UK Class 4 NI (9% on profits £12,570–£50,270, then 2% above that) instead of US SE tax. You need to obtain a Certificate of Coverage from HMRC (form CA3821) to document this. Then on your US return, you claim the exemption under the totalization agreement.
⚠️ The gap: If you're doing occasional contractor work and don't formally register as self-employed with HMRC, you might not be paying UK NI — which means the exemption may not apply and you could owe US SE tax. Register with HMRC as self-employed (it's free and takes 10 minutes at gov.uk) before the tax year ends.
| Action | UK Side | US Side |
|---|---|---|
| Register as self-employed | HMRC — gov.uk, free | No registration needed; report on Schedule C |
| Pay income tax | UK Self Assessment, annual return | Claim Foreign Tax Credit (Form 1116) |
| Social security / NI | Class 4 NI via Self Assessment | Claim SE tax exemption (Totalization Agreement) |
| Documentation | Keep invoices, receipts | Certificate of Coverage from HMRC (CA3821) |
| Deadlines | UK Self Assessment: Jan 31 each year | US return: June 15 (auto) + FBAR: April 15 |
If you're working as an independent contractor for a US company (not as an employee), they'll likely ask you to complete a W-8BEN form (for individuals). This certifies you're a non-US-resident for withholding purposes — but here's the catch: as a US citizen, technically a W-8BEN may not apply to you. US citizens typically complete a W-9 instead.
Most US companies will issue you a 1099-NEC at year end showing your total earnings. You include this on your US Schedule C, then offset the resulting tax with your FTC from UK taxes paid.
"If you are self employed (aka a contractor) you will still need to pay 15.3% for employee and employer portion of FICA (SS & Med) plus your income taxes unless you are exempt from SE tax via a totalization agreement."
Honestly — for basic self-employment income, probably not in year one, especially if your income is under £50,000. The mechanics are well-documented. Tools like MyExpatTaxes (~$200/year) handle the FTC calculation and SE tax exemption automatically.
You'd want a specialist if you have:
💸 Getting paid in USD from UK? Use our transfer calculator to find the cheapest way to convert USD earnings to GBP — bank FX markups can eat 2–3% of every payment.
Compare Transfer Rates →📌 Bottom line: The system is designed to prevent double taxation. It requires paperwork and awareness, but you won't end up paying 50%+ on your income if you follow the steps. The real risk is not registering and not filing — penalties for missing US returns while abroad can be severe even if no tax is owed.