Compare ETFs on a UK broker and many well-known US funds are missing. The reason is regulatory. The bigger surprise is that tax rules can catch out even UCITS ETFs that are available, because the treatment depends on a status the fund has to hold with HMRC.
What is a UCITS ETF?
A UCITS ETF is an ETF built on a fund framework that started in the EU and sets minimum standards for investor protection. UCITS stands for "Undertakings for Collective Investment in Transferable Securities." Many of the ETFs listed in London are UCITS funds, often domiciled in Ireland or Luxembourg, and they carry "UCITS ETF" in the name.
The framework includes diversification limits. As a general rule, a UCITS may put no more than 5% of its assets into one issuer. Member states may raise that to 10%, provided all holdings above 5% together stay under 40%. Index-tracking UCITS may go up to 20% in a single issuer, and up to 35% where justified by exceptional market conditions (Directive 2009/65/EC, Articles 52 and 53).
Why can't most UK retail investors buy US-domiciled ETFs?
Because most of them do not publish a Key Information Document (KID). Since 1 January 2018, packaged investment products sold to retail investors have needed one, and the FCA requires it to be provided to a retail investor in good time before a transaction. UK platforms therefore generally do not offer US-domiciled ETFs to retail clients.
The rulebook is changing. The FCA's Consumer Composite Investments (CCI) regime replaced the UK PRIIPs Regulations on 6 April 2026. Manufacturers can keep using existing disclosure documents until the new rules apply in full on 8 June 2027, when a CCI product summary takes over from the KID and the UCITS KIID (FCA policy statement PS25/20). The regime is new, so check your broker's current product list instead of assuming that US funds have become available.
What is the reporting fund tax trap?
For a UK taxpayer, HMRC reporting fund status decides how an offshore fund's gains are taxed. Funds domiciled outside the UK, including Irish and Luxembourg UCITS ETFs and US-domiciled ETFs, fall under HMRC's offshore fund rules. A fund is either a reporting fund or a non-reporting fund.
HMRC describes the difference like this:
- Reporting fund: you pay tax on your share of the fund's reportable income, even if it is not paid out. Gains when you sell are taxed as capital gains. In the 2026 to 2027 tax year, capital gains tax is 18% or 24% above the £3,000 annual exempt amount, depending on your income tax band (gov.uk).
- Non-reporting fund: you are taxed only on income the fund actually distributes. A gain when you sell is normally an "offshore income gain" and is taxed as income rather than as a capital gain.
Income tax rates are usually higher than capital gains rates, so the gap can be large. This applies to UCITS ETFs too: UCITS status does not equal reporting status. Check each fund on HMRC's list of reporting funds instead of relying on the name. Many US-domiciled ETFs are not on it.
Accumulating reporting funds have their own quirk. Even though the fund never pays you anything, HMRC treats the "excess reported income" as received on the fund's distribution date, which is six months after the end of its reporting period. Outside an ISA, you declare it on the foreign pages of your Self Assessment return, usually as dividends.
You are taxed each year on money you never received in cash. The amount is later added to your cost base so that it is not taxed twice.
Do ISAs and SIPPs avoid the reporting fund issue?
Mostly, in an ISA. Holdings inside a Stocks and Shares ISA are not reported on your tax return: according to HMRC, if you hold a reporting or non-reporting offshore fund through an ISA, you do not need to declare the income or gains. Pensions such as a SIPP are also tax-advantaged wrappers, although the rules differ, so read the terms of yours. The reporting status question matters most in a general investment account.
What do US dividend withholding and US estate tax add?
US-domiciled funds and US shares pay dividends after US withholding tax, at a default rate of 30% for foreign investors. UK residents can usually reduce it to 15% under the UK-US tax treaty by giving their broker a W-8BEN form. You may then be able to claim a credit for the US tax against UK tax on the same dividend, though the credit cannot exceed the UK tax due on it.
US estate tax is a separate issue. The IRS says an executor of a non-US, non-citizen decedent must file a US estate tax return if US-situated assets exceed $60,000 at death, and shares in US companies count as US-situated. Whether and how this applies to a US-domiciled ETF depends on the asset and on any treaty, so get advice before holding US-domiciled funds directly.
What should you check before buying an ETF?
Three things. First, that your broker offers the fund to retail clients. Second, that the fund has UK reporting fund status for the years you will hold it. Third, whether you hold it in an ISA or pension or in a taxable account, because that decides how much the reporting rules affect you.
A UCITS ETF with reporting status is the simplest case for most UK investors, and it is what most large index funds are.
Picking an ETF doesn't settle position size
Whichever fund you choose, how large one position should be relative to your portfolio is a separate decision. Axiomly's position size calculator is free and works out the numbers regardless of the product. This article is educational and not tax advice, so check your own tax situation on gov.uk or with a qualified adviser.