UK Inheritance Tax vs US Estate Tax: What Americans With UK Property Need to Know
How UK Inheritance Tax and US Estate Tax interact for Americans owning UK property, including the 1979 treaty, domicile rules and double taxation relief.
Raju GajurelJul 18, 2026Updated Jul 20, 2026
For US citizens who own property in the UK, death can trigger a tax problem most people never see coming: two separate tax authorities, each able to tax the same estate under rules built decades apart. The IRS taxes a US citizen's worldwide estate; HMRC taxes UK-situated assets, and potentially the worldwide estate where the deceased was UK domiciled or deemed domiciled. Knowing where the two regimes overlap, and where the 1979 treaty steps in, is essential for anyone splitting their life and their assets between the UK and the US.
Key takeaways
- UK Inheritance Tax bites far sooner than US estate tax: a frozen £325,000 nil-rate band at 40%, versus a $15 million US exemption in 2026.
- Domicile decides scope. UK real estate is always within IHT; being UK domiciled or deemed domiciled pulls in the worldwide estate too.
- Since 6 April 2025, long-term UK residence (not intent to stay) can create deemed domicile and expose worldwide assets.
- The 1979 UK-US estate tax treaty and HMRC's Unilateral Relief prevent the same asset being taxed in full twice, via a capped credit.
- US and UK wills, structures and elections must be coordinated. Optimising one side alone can raise the overall bill.
The core mismatch: two very different thresholds
The first thing that catches Americans out is scale. Under the Inheritance Tax Act 1984, the UK nil-rate band has been frozen at £325,000 since 2009, with a further residence nil-rate band of up to £175,000 where a home passes to direct descendants. Anything above the available threshold is generally taxed at 40%.
The US federal estate tax exemption is far larger. For deaths in 2026 it stands at $15 million per individual, or up to $30 million for a married couple using portability, with a 40% rate above that level. An estate that comfortably clears the US threshold can still generate a significant UK Inheritance Tax bill on a single London flat.
| Feature | UK Inheritance Tax | US Estate Tax |
|---|---|---|
| Tax-free threshold | £325,000 nil-rate band (+ up to £175,000 RNRB) | $15m per person (2026) |
| Headline rate | 40% | 40% |
| Scope driver | Domicile / deemed domicile | US citizenship / residence |
| Worldwide reach | If UK domiciled or deemed domiciled | Always, for US citizens |
| Spouse transfers | Exempt, but capped to a non-UK-domiciled spouse | Unlimited to US-citizen spouse |
Why domicile decides so much
HMRC's charge to Inheritance Tax depends heavily on domicile. A non-UK domiciled individual is generally taxed only on UK-situated assets, such as UK real estate. Someone who is UK domiciled, or deemed domiciled, is taxed on their worldwide estate instead.
This matters more than ever since 6 April 2025, when the old 15-out-of-20-year deemed domicile test was replaced by a residence-based long-term UK resident test. A US citizen who has lived in the UK for an extended period can be treated as UK domiciled for Inheritance Tax purposes without ever intending to settle permanently, exposing worldwide assets, not just the UK property, to a UK charge.
The 1979 UK-US estate tax treaty
The UK and US have had a double taxation convention covering estates, gifts and inheritances in force since 11 November 1979, one of only a handful of such treaties the UK holds. Broadly, it allows the country where the deceased was domiciled to tax the whole estate, while the other country taxes only specified property in its own territory, such as immovable property. Where both countries still charge tax on the same asset, the treaty (or, failing that, HMRC's Unilateral Relief) provides a credit so the same value is not taxed twice in full.
Worked example (HMRC)
On a £500,000 estate that includes a $35,000 (£35,000) American apartment, the Inheritance Tax due is £70,000, of which £4,900 is attributable to the US property under the formula A ÷ (A + B) × C. If $1,500 of American tax was actually paid on that apartment, the UK credit is capped at that £1,500, not the full £4,900 theoretically attributable.
Practical planning points
- Check domicile status carefully. Long-term UK residence can trigger deemed domicile and expose worldwide assets to UK Inheritance Tax.
- Revisit spousal transfers. The unlimited spouse exemption is restricted where one spouse is non-UK domiciled, so cross-border couples can face an unexpected charge on the first death.
- Use the treaty deliberately. Relief must be claimed and evidenced with the tax actually paid overseas, it does not apply automatically.
- Coordinate wills on both sides of the Atlantic. A will drafted for US probate can create unintended UK Inheritance Tax consequences, and vice versa.
- Review how UK property is held. Personal, company or trust ownership changes both the UK IHT and US estate tax analysis, and interacts with ATED and CGT.
Frequently asked questions
Will my UK property be taxed by both the UK and the US?
I'm a US citizen who has lived in the UK for years. Does that affect my Inheritance Tax position?
Is the US estate tax exemption really $15 million?
Does the spouse exemption always apply?
How do I claim double taxation relief?
US citizen with UK property?
We help internationally mobile individualsls|individuals]] plan UK Inheritance Tax alongside US estate tax so the two systems work together, not against each other. Speak to us before it becomes an estate administration problem.
Speak to a cross-border tax specialistThis article is general guidance, not personalised tax advice, and reflects the rules in force at the time of writing. Speak to a chartered tax adviser about your specific circumstances.
