Going self-employed in the UK as an American means stepping into two tax systems at once — and the good news is that, handled correctly, the overlap is far less painful than people fear. The headline relief is significant: most self-employed Americans in the UK are exempt from US self-employment tax, a 15.3% charge, thanks to a treaty most people have never heard of. This guide explains your obligations in both countries and how to claim that exemption.
The short answer
A US citizen self-employed in the UK files in both countries, but the US-UK Totalization Agreement usually exempts you from US self-employment tax (SECA). You report your UK self-employment profit on a US return (Schedule C) and on UK Self Assessment; UK income tax and National Insurance apply, and the Foreign Earned Income Exclusion or Foreign Tax Credit typically offsets the US income tax. Critically, because you're UK-resident and self-employed, you pay UK National Insurance instead of US self-employment tax — proven with an HMRC certificate of coverage.
Key takeaways
- You file in both countries: UK Self Assessment and a US return (Schedule C).
- The Totalization Agreement usually exempts you from US self-employment tax (15.3%).
- You pay UK National Insurance instead, evidenced by an HMRC certificate of coverage.
- The FEIE removes US income tax but not self-employment tax — only the treaty does that.
- UK income tax is usually offset on the US side by the FEIE or Foreign Tax Credit.
Executive summary
For a self-employed American in the UK, the obligations split cleanly into two layers. On income tax, you're taxed by both countries, but the Foreign Earned Income Exclusion or Foreign Tax Credit usually eliminates the US income tax, since UK rates are comparable or higher. On social security, the US would normally charge self-employment tax (SECA) at 15.3% — but the US-UK Totalization Agreement assigns a UK-resident self-employed person to the UK system, so you pay UK National Insurance instead and obtain an HMRC certificate of coverage as proof. The most common, costly error is assuming the FEIE removes the self-employment tax (it doesn't) or simply not obtaining the certificate. Get both layers right and the US burden is largely procedural.
Layer one: income tax in both countries
As a US citizen, you report worldwide income, so your UK self-employment profit appears on a US return — generally on Schedule C, the US form for sole-proprietor business income. You'll separately report the same profit through UK Self Assessment.
The same income being taxed twice sounds alarming, but the US side is usually neutralised by one of two tools:
- the Foreign Earned Income Exclusion, which can exclude a capped amount of foreign earned income; or
- the Foreign Tax Credit, which credits the UK tax you paid against your US tax.
For most self-employed Americans in the UK, one or both of these reduces the US income tax to little or nothing. (Which to use is its own decision — see FEIE or Foreign Tax Credit.)
Layer two: the self-employment tax exemption (the valuable bit)
Here's the relief that matters most. In the US, a self-employed person normally pays self-employment tax (SECA) at 15.3% — covering Social Security and Medicare — on top of income tax. If that applied to your UK profits, self-employment in the UK would be punishingly expensive on the US side.
It usually doesn't apply, because of the US-UK Totalization Agreement (1984). The agreement's rule for the self-employed is deliberately simple: coverage follows the country of residence. A US citizen genuinely resident in the UK and self-employed here is assigned to the UK system — so you pay UK National Insurance and are exempt from US self-employment tax on those earnings.
There's an important technical subtlety worth stating plainly: under the agreement, the US charge is removed, not credited. This isn't a foreign tax credit mechanism — the US self-employment tax simply doesn't apply, provided you can evidence UK coverage.
The certificate of coverage — don't skip this
The exemption isn't automatic. From the US perspective, self-employment tax continues to apply unless you can prove you're covered by the UK system. The proof is a certificate of coverage obtained from HMRC, confirming you're subject to UK National Insurance. You then attach it to your US return.
In practice:
- apply through HMRC's "National Insurance when abroad" service;
- attach the certificate to your US return each year;
- you generally do not complete Schedule SE (the US self-employment tax schedule), instead noting the treaty exemption.
This is administrative, not conceptual — but missing it can mean paying a 15.3% tax you didn't owe.
UK National Insurance for the self-employed
On the UK side, a self-employed sole trader generally pays Class 4 National Insurance on profits through Self Assessment. Class 2 National Insurance was abolished from April 2024, though contributions above a profits threshold are still treated as made to protect your State Pension entitlement. Because the rates and thresholds here change at fiscal events, we deliberately avoid quoting specific figures — confirm the current Class 4 rate and thresholds for your tax year.
One useful benefit point: your UK National Insurance contributions count toward your UK State Pension, and under the Totalization Agreement your US and UK credits can be combined when assessing future benefit eligibility.
Common mistakes we see
- Paying US self-employment tax unnecessarily by not obtaining the certificate of coverage.
- Assuming the FEIE removes self-employment tax — it removes income tax only.
- Not filing UK Self Assessment, or not filing the US return, on the belief that one covers the other.
- Relying on old National Insurance guidance that predates the Class 2 abolition.
- Forgetting the certificate is annual — it's not a one-time setup.
Related reading
- Sole trader or limited company for an American in the UK? — whether to stay self-employed or incorporate.
- Freelancer or contractor in the UK: what US tax forms do you need? — the US forms checklist for independent workers.
- FEIE or Foreign Tax Credit: which should I use in the UK? — choosing the right income-tax relief.
This article is general information, not personalised advice. Your exact UK and US obligations as a self-employed American depend on your residence, profit and circumstances, and the certificate-of-coverage process must be done correctly each year. Book a free consultation and we'll make sure your UK and US filings align and you claim every exemption you're entitled to.