A self-employed US citizen in the UK files twice: Schedule C in dollars on Form 1040, and Self Assessment in pounds with HMRC. The one that costs real money is US self-employment tax at 15.3%, which the foreign earned income exclusion does not touch — only a certificate of coverage removes it. UK tax for US citizens sets the frame.
Employees rarely meet this problem, because their UK employer takes National Insurance and the treaty sorts the rest. Sole traders and freelancers hit it in their first year, usually after the return has already been filed the wrong way.
Self-employed in the UK: what each country charges
| Charge | Rate | Applies to |
|---|---|---|
| US federal income tax | Graduated | Worldwide profit, relieved by exclusion or credit |
| US self-employment tax | 15.3% up to the wage base, 2.9% above | Net earnings, unless a certificate of coverage applies |
| UK income tax | 20%, 40%, 45% | Profit above the personal allowance |
| Class 4 National Insurance | 6% from £12,570 to £50,270, then 2% | Profit for 2026-27 |
| Class 2 National Insurance | Treated as paid at £7,105 of profit; £3.65 a week voluntarily below that | Your contribution record |
| VAT | 20% standard | Turnover above £90,000 on a rolling 12 months |
GOV.UK publishes the current self-employed National Insurance rates and the VAT registration rules, including the forward-look test that catches a business about to cross £90,000 in the next 30 days.
Self-employment tax is the real exposure
US self-employment tax is not income tax, and none of the usual expat reliefs reduce it. You can exclude every dollar of profit under the foreign earned income exclusion and still owe 15.3% of your net earnings, because the exclusion applies to income tax alone.
The foreign tax credit does not help either. National Insurance is not creditable, and UK income tax cannot be credited against a US social security charge. Without a certificate, you pay into two social security systems on the same profit.
The certificate of coverage
The US–UK totalization agreement assigns you to one system. A self-employed person living in Britain is normally covered by the UK system, and HMRC issues a certificate of coverage confirming it — which is what exempts you from US self-employment tax.
The IRS explains the mechanism on its page for totalization agreements. In practice you apply to HMRC, keep the certificate, and attach a statement to Form 1040 claiming the exemption, rather than simply leaving Schedule SE blank. Our guide to the US–UK totalization agreement covers how coverage is assigned.
The certificate assigns social security coverage only. It does not affect income tax, the treaty position on your profit, or anything else on the return.
Building Schedule C from UK records
Your Schedule C is not a translation of your Self Assessment figures. The two systems allow different deductions, run on different years, and use different currencies, so the profit figure rarely matches.
- UK tax year runs 6 April to 5 April; Schedule C covers the calendar year.
- The UK trading allowance and cash basis have no US equivalent.
- Capital allowances differ from US depreciation, including bonus depreciation and section 179.
- Mileage and home-office rates are set separately by each country.
- VAT collected is not income and VAT paid is not a deduction where it is recoverable.
- Translate at the rate on the date of each transaction, or a consistent yearly average where income is earned evenly.
When a company starts to make sense
Incorporating a UK limited company changes the analysis completely. The profit belongs to the company, US self-employment tax falls away, and in its place come the controlled foreign corporation rules, Form 5471 and the NCTI regime — set out in US owners of UK companies.
That is a trade, not an upgrade. A company suits established profits and long horizons; the compliance cost is real and the filing obligations are annual. For many freelancers, staying a sole trader with a certificate of coverage is the cheaper answer.
The filing calendar
Both systems want returns, on dates that do not align. The US return is due 15 April with the automatic expat extension to 15 June and Form 4868 to 15 October; UK Self Assessment is due by 31 January online, with payments on account in January and July — the full picture is in US expat tax deadlines for 2026.
The UK side starts earlier than most people expect. GOV.UK's guidance on how to set up as a sole trader requires registration for Self Assessment once you earn more than £1,000 in a tax year, and you can register sooner. Payments on account then arrive in two instalments, each half of the previous year's liability, which is what makes a first full year of trading feel like eighteen months of tax at once.
Add the reporting: a business account abroad counts for the FBAR at the same $10,000 aggregate threshold as a personal one, and it is the peak balance that matters.
Tranzesta prepares Schedule C and Self Assessment from one set of records, with the certificate of coverage in place before the first US return is filed. Book a consultation if you are freelancing in Britain on a US passport.
Frequently Asked Questions
Do I pay US self-employment tax if I live in the UK?
Not if the US–UK totalization agreement assigns you to the UK system and you hold a certificate of coverage from HMRC. Without that certificate you owe US self-employment tax at 15.3% on net earnings even if all of your profit is excluded under the foreign earned income exclusion, because the exclusion applies only to income tax.
Does the foreign earned income exclusion cover self-employment tax?
No. The exclusion removes foreign earned income from your taxable income for income tax purposes only. Self-employment tax is a social security charge computed on net earnings from self-employment, and neither the exclusion nor the foreign tax credit reduces it.
How do I get a certificate of coverage?
A self-employed person living in the United Kingdom applies to HMRC, which issues the certificate confirming that UK National Insurance covers them. You keep the certificate and attach a statement to your Form 1040 claiming exemption from US self-employment tax under the agreement, rather than simply omitting Schedule SE.
Do I have to register for UK VAT?
You must register if your taxable turnover exceeded £90,000 over the last 12 months, or if you expect to cross £90,000 in the next 30 days. The test is rolling rather than annual, so a strong few months can trigger registration part way through a year even if the year as a whole is below the threshold.
Is my Schedule C profit the same as my Self Assessment profit?
Usually not. The tax years differ, the currencies differ, and the deduction rules differ — UK capital allowances and the trading allowance have no direct US equivalent, and US depreciation rules have no UK equivalent. Each return should be built from the underlying records rather than by translating the other country's profit figure.
What if I am self-employed in Dubai instead?
There is no totalization agreement between the United States and the UAE, so a certificate of coverage is not available and US self-employment tax applies to your net earnings in full. The foreign earned income exclusion can still remove the income tax, but the 15.3% charge remains, which is why many US freelancers in the UAE consider incorporating.
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