EIS and SEIS for US citizens produce a genuine tax benefit in Britain and almost none in America. HMRC gives you 30% income tax relief on an Enterprise Investment Scheme subscription and 50% on a Seed Enterprise Investment Scheme subscription, exempts the gain entirely after three years, and lets you set a loss against income at your marginal rate. The Internal Revenue Service mirrors none of that. It taxes the exit, ignores the relief, and — where the shares meet the passive foreign investment company definition — applies a punitive regime with its own annual form.
The practical result is that an American in London can make a 30% paper return on day one, pay no UK tax on the exit five years later, and still hand a large slice of the proceeds to the IRS with no foreign tax credit to shelter it. That is not a reason never to invest. It is a reason to size the position, choose the structure and time the claim with both tax systems on the table at once.
What EIS and SEIS actually give a UK investor
Start with the British half of the picture, because it is the half that works. HMRC's guidance on tax relief for investors using venture capital schemes sets out five distinct reliefs, and most investors only think about the first.
The income tax relief is a reduction in your liability, not a deduction from income, so it is worth the same to a basic-rate and an additional-rate taxpayer in cash terms — but it is capped at the tax you actually owe. An American in the UK claiming large foreign tax credits and substantial pension relief may find their UK liability is already low enough that a full EIS claim cannot be absorbed in the year.
- SEIS income tax relief at 50% on up to £200,000 subscribed in a tax year.
- EIS income tax relief at 30% on up to £1,000,000, rising to £2,000,000 where the excess is in knowledge-intensive companies.
- Disposal relief — no UK capital gains tax on the growth, provided income tax relief was given, not withdrawn, and the shares are held for at least three years.
- EIS deferral relief, which postpones a separate capital gain by reinvesting it; and SEIS reinvestment relief, which exempts 50% of a gain reinvested into SEIS shares.
- Share loss relief, which lets a loss net of income tax relief be set against income in the year of loss or the year before, at your marginal rate.
- A carry-back facility that treats the subscription as made in the previous tax year, subject to that year's limits.
What changed on 6 April 2026
Two sets of changes matter for anyone investing now. First, the sunset clauses that would have ended income tax relief for shares issued after 5 April 2025 have been extended to 6 April 2035, so EIS and the Venture Capital Trust scheme have a decade of statutory life ahead of them.
Second, from 6 April 2026 the company-side limits roughly doubled while the VCT relief rate was cut. Under the published measure on the EIS and VCT investment limit increase, the annual amount a qualifying company can raise rose from £5 million to £10 million, and from £10 million to £20 million for a knowledge-intensive company. The lifetime limits rose from £12 million to £24 million, and from £20 million to £40 million for knowledge-intensive companies. Gross asset limits moved from £15 million to £30 million before the share issue and from £16 million to £35 million after it.
The investor-side annual limits were not increased — £1 million, or £2 million with knowledge-intensive companies, remains the EIS ceiling, and £200,000 remains the SEIS ceiling. What changed is the size and maturity of the companies you can now back with relief attached, which pushes EIS further into later-stage territory. For a US citizen that is a double-edged development: a larger, more established company is less likely to fail the passive asset test, but a larger raise also makes it easier for a single investor to cross an American ownership threshold without noticing.
Why EIS and SEIS for US citizens goes wrong
The United States taxes its citizens on worldwide income regardless of where they live, and it recognises only the reliefs written into its own code or into the treaty. There is no article of the US–UK treaty that imports EIS or SEIS relief, and the saving clause preserves America's right to tax its own citizens as if much of the treaty did not exist. So the reliefs do not transfer.
That produces three separate problems, and they compound. The UK relief reduces the UK tax you pay, which reduces the foreign tax credit you can claim in America. The UK exemption on exit removes the UK tax entirely, leaving the US gain wholly unsheltered. And the shares themselves may fall inside the PFIC regime, which changes the calculation from a simple capital gain into an interest-charged excess distribution computation.
None of these is exotic. All three routinely appear on the same return, in the same year, for the same investment.
The income tax relief that quietly costs you a foreign tax credit
Foreign tax credit relief works on tax actually paid or accrued. Claim £30,000 of EIS relief against a UK bill and you have reduced the pool of British tax available to offset your American liability by £30,000. If your US tax on the same income was going to be covered by surplus UK tax, that surplus has just shrunk.
For a high earner in London with a large general-limitation credit carryforward, this may cost nothing today — the credits are simply used at a different rate. For an American whose UK and US liabilities run close together, particularly one relying on the foreign earned income exclusion for salary and credits for investment income, the EIS claim can convert a comfortable position into a US balance due. Modelling the credit position before claiming is the whole game; our foreign tax credit calculator will show you where the limitation bites.
There is also a timing dimension. The carry-back facility lets you treat the subscription as made in the previous tax year. That can rescue an unused UK liability, but it also moves the credit consequence into a US year you have already filed, which may mean an amended Form 1040 and a foreign tax redetermination rather than a clean current-year adjustment.
The tax-free UK exit that the IRS taxes in full
Disposal relief is the most valuable EIS benefit and the most dangerous one for an American. Hold qualifying shares for three years with income tax relief intact and the entire gain escapes UK capital gains tax. There is then no UK tax on that gain — and therefore nothing to credit against the US tax on the same gain.
An American who turns a £100,000 EIS subscription into a £600,000 exit pays nothing in Britain and faces US federal tax on a $500,000-equivalent long-term gain, plus the 3.8% net investment income tax, with no offsetting credit whatsoever. The headline UK benefit has, in effect, been transferred to the US Treasury.
This is the single most common surprise we see. Investors model the UK outcome, see zero, and assume zero. Run the same disposal through our UK capital gains tax calculator and then price the US side separately — the two numbers do not net off, they stack.
PFIC: when the shares themselves are the problem
A foreign corporation is a passive foreign investment company if 75% or more of its gross income for the year is passive, or if 50% or more of the average value of its assets produce, or are held for the production of, passive income. The IRS explains the mechanics and the elections on its Form 8621 instructions page. Cash counts as a passive asset.
That last point is what catches early-stage investors. A start-up that has just closed a £4 million round is, by definition, sitting on £4 million of cash and very little else. Measured on average asset value across the year, it can easily be more than half passive — not because it is an investment vehicle, but because it has just been funded and has not spent the money yet.
Once a company is a PFIC in a year during which you hold shares, the default excess distribution regime applies on disposal: the gain is spread rateably over your holding period, taxed at the highest ordinary rate for each earlier year, and an interest charge is added for the deferral. The long-term capital gain rate does not apply. Our detailed comparison of the mark-to-market and QEF elections sets out the two ways out, and why the QEF election is usually unavailable in practice for a private company that will not produce a PFIC annual information statement.
The start-up exception is narrower than people think
There is a start-up exception. A corporation is not treated as a PFIC for the first tax year in which it has gross income, provided no predecessor was a PFIC, and provided it is established that the corporation will not be a PFIC for either of the two following years and it is in fact not a PFIC for those years.
Read the conditions carefully. The relief covers one year, not the funding period. It is conditional on the two following years actually being clean, so it can be lost retrospectively if the company raises a large round and sits on the proceeds. And it requires a factual case about future years that a passive minority investor is in no position to establish, because the information sits with the company.
In practice, the exception saves the genuinely fast-trading start-up that deploys its cash quickly and generates operating revenue. It does not save the deep-tech company that raises £15 million and spends it over four years, and it does not save the investor who has no visibility over the company's balance sheet composition.
EIS funds, VCTs and portfolio services
Direct subscription into a single trading company at least has an argument. A pooled vehicle does not. An EIS fund, an approved knowledge-intensive fund, a VCT and most managed EIS portfolio services are collective investment vehicles whose income and assets are overwhelmingly passive. They are PFICs, and a portfolio service holding fifteen underlying companies may generate fifteen separate PFIC positions rather than one.
Each PFIC interest is reported on its own Form 8621. Fifteen positions is fifteen forms a year, each requiring the underlying company's figures, with the excess distribution computation carried across the whole holding period. The compliance cost alone frequently exceeds the UK relief on a moderate subscription.
This is the same structural problem Americans hit with stocks and shares ISAs and UK-domiciled funds, which we cover in why UK ISAs fall into the PFIC rules. The wrapper differs; the analysis does not.
Loss relief: generous in Britain, capped in America
Roughly half of all EIS and SEIS investments lose money, which is why UK share loss relief matters so much. Set the loss net of income tax relief against income at 45% and an additional-rate taxpayer's total downside protection on an EIS investment reaches around 61.5% of the sum invested; on SEIS, where the initial relief is 50%, it is higher still.
America is far less generous. A loss on stock is a capital loss. Capital losses offset capital gains without limit, but only $3,000 a year can be set against ordinary income, with the excess carried forward. The two specifically generous US provisions do not help: section 1244 ordinary loss treatment applies only to stock in a domestic corporation, and the qualified small business stock exclusion under section 1202 likewise requires a domestic C corporation — a point we set out in full in the QSBS exclusion after the 2026 rules.
So the British system gives you a fast, full-rate deduction and the American system gives you a $3,000 annual trickle. If the shares are also a PFIC, a loss under the excess distribution regime does not even generate the deduction you would expect, because the regime is built to tax gains rather than recognise losses.
The 10% ownership line that turns an investment into Form 5471
EIS relief requires that you are not connected with the company, which broadly means holding no more than 30% of the ordinary share capital, voting power or assets on a winding up. That leaves a wide band between a small stake and 30% in which an American investor can quietly become a US shareholder of a controlled foreign corporation for American purposes.
Cross 10% of vote or value and you are a Category 5 filer on Form 5471 if the company is a controlled foreign corporation — that is, if US shareholders holding 10% or more together own more than 50%. In a UK seed round with several American angels, that combination is not unusual. The consequences run well beyond a form: net CFC tested income inclusions, subpart F, and the possibility of a section 962 election to access corporate rates.
We deal with the mechanics in Form 5471 for Americans owning UK companies. The point for an EIS investor is simply that the 30% UK ceiling and the 10% US threshold are three times apart, and only one of them appears in the fund documentation.
Currency: dollars decide your gain, not pounds
Your US gain is computed in dollars. Basis is fixed at the exchange rate on the date of subscription; proceeds are translated at the rate on the date of disposal. A holding that produced a modest sterling gain can produce a large dollar gain, or the reverse, purely on sterling's movement.
For an EIS investor this bites hardest precisely where the UK relief is most valuable — the exempt exit. There is no UK tax to credit, so the entire dollar gain, currency element included, is taxed in America at full rate. A 15% move in the exchange rate over a five-year hold is ordinary, and on a large exit it is the difference between a manageable US bill and a serious one.
The same logic runs in reverse on a loss. A sterling loss can be a smaller dollar loss, and where the dollar loss is smaller the already-limited US relief shrinks further.
Inheritance tax, business relief and the estate tax overlay
Unquoted trading company shares held for at least two years have historically qualified for 100% business relief from UK inheritance tax, which made EIS portfolios a common estate planning tool. That changed from 6 April 2026. Under the reforms to agricultural property relief and business property relief, 100% relief now applies only up to a combined allowance — raised to £2.5 million in the announcement of 23 December 2025 — with 50% relief above it, producing an effective rate of up to 20% rather than a full exemption.
For an American this is layered on top of US estate tax, which applies to a citizen's worldwide estate with a basic exclusion amount of $15,000,000 for deaths in 2026. UK business relief does not reduce the US estate tax base, and the interaction of the two systems is governed by the separate US–UK estate and gift tax treaty rather than the income tax treaty.
The result is that EIS shares can sit inside both estates at once, with partial relief in one and none in the other. Our comparison of US estate tax and UK inheritance tax sets out how the two regimes are reconciled and where they simply are not.
What an EIS portfolio adds to your US return
Shares in a private UK company held for investment are specified foreign financial assets and are reported on Form 8938 once you cross the threshold — $200,000 at year end or $300,000 at any point in the year for a single filer living abroad, doubled for a joint return.
They are generally not FBAR items, because the FBAR reports financial accounts rather than directly held securities. But an EIS portfolio service or nominee arrangement often is an account, and where the shares sit in a UK platform or nominee wrapper the FBAR obligation can attach to the wrapper even though the underlying shares would not be reportable on their own.
Add a Form 8621 for each PFIC position, a Form 5471 if you cross 10% of a controlled foreign corporation, and a Form 8938 schedule listing every holding, and a £50,000 EIS allocation can add more pages to a Form 1040 than the rest of the return combined.
How to invest in UK start-ups without wrecking your US return
None of this makes EIS and SEIS off-limits. It makes them a decision that has to be priced on an after-US-tax basis, which almost no UK adviser will do for you and almost no fund brochure will mention.
The investors who handle this well tend to do the same handful of things: they subscribe directly rather than through funds, they stay well under 10% of vote and value, they document the company's income and asset profile from the start so the PFIC position is a matter of record rather than reconstruction, and they model the foreign tax credit consequence before making the UK claim rather than after.
Work out the UK relief first with our EIS and SEIS tax relief calculator, then hold that figure up against the US cost of the same investment. If the answer is still positive, you have a good investment. If it is not, you have learned it before the money left your account rather than five years later.
- Prefer direct subscriptions in single trading companies over EIS funds, VCTs and managed portfolio services.
- Keep each holding below 10% of vote and value to stay outside the CFC and Form 5471 regime.
- Negotiate annual PFIC information rights into the subscription documents before you sign.
- Model the foreign tax credit effect of the UK claim, including any carry-back, before making it.
- Price the exempt UK exit as a fully taxable US disposal, and keep dollar basis records from day one.
- Review the position annually — a company that was outside the PFIC tests in year one can fall inside them in year three.
