UK-US estate and inheritance tax treaty: Complete guide
The UK–US estate and inheritance tax treaty (often referred to as the UK US inheritance tax treaty, separate from the income tax treaty) helps prevent double taxation on estates, gifts, and inheritances when someone has assets or connections in both countries. It coordinates taxing rights using treaty domicile rules and provides credit relief when both countries tax the same property.
Quick reference: estate tax treaty benefits
| Without Treaty | With Treaty |
|---|---|
| Both countries tax worldwide estates | Treaty domicile determines primary taxing country |
| US: $60K exemption for non-domiciliaries | Pro rata credit increases exemption to $300K+ |
| UK: 10-year long-term resident tail | Treaty domicile can reduce to 3 years |
| Potential 40% (US) + 40% (UK) on the same assets | Tax credits prevent double taxation |
These coordination rules are at the core of the UK–US inheritance tax treaty, particularly for families exposed to both US estate tax and UK IHT.
NOTE! The estate and gift tax treaty coordinates through domicile rules and tax credits. Domicile is determined by Article 4 – for details on tie-breaker tests, see our US–UK tax treaty guide.
How the estate tax treaty works
The UK–US estate and inheritance tax treaty assigns which country has primary taxing rights based on treaty domicile and property type, then reduces double taxation through credit rules.
It also includes special rules for certain trusts and spouse transfers that can materially change the taxable estate in cross-border situations.
Also read. Taxes in the UK vs. the US
Treaty domicile and taxing rights
Treaty domicile is the treaty’s “control switch.” Once treaty domicile is determined, one country generally has the primary right to tax worldwide transfers, while the other country’s taxing rights are more limited (often to property located in that country). This coordination is designed to reduce double taxation.
Your treaty domicile determines which country has primary rights to tax your worldwide estate:
- US treaty domicile: the US generally taxes the worldwide estate; the UK’s taxing rights are generally more limited to UK-connected property.
- UK treaty domicile: the UK generally taxes the worldwide estate; the US generally limits its reach to US-situs property.
High-level tie-breaker only: Article 4 uses a sequence of tests (home, closer personal/economic ties, habitual abode, nationality, and competent authority agreement).
Tax credits (Article 9)
When both countries tax the same property transfer, Article 9 coordinates foreign tax credits so you don’t pay “full tax twice.” The credit is generally limited to the tax attributable to the overlapping property, and the treaty also includes time limits and procedural requirements for claiming relief.
How the credit works
The credit is typically the lesser of:
- foreign tax paid on the property, or
- the domestic tax attributable to that same property.
Automatic relief claimed on estate tax returns (Form 706 in the US, IHT400 in the UK)
Pro rata unified credit for non-domiciliaries (Article 9A)
Key benefit for cross-border estates:
- Standard rule: Non-US domiciliaries get only a $60,000 exemption for US assets.
- Treaty benefit: UK domiciliaries can claim a proportional exemption.
- Formula: Exemption = $13.99M × (US assets ÷ worldwide estate).
- Example: £10M worldwide estate, £2M US stocks ($2.5M). Pro rata = $13.99M × ($2.5M ÷ $12.5M) = $2.8M exemption. Saves $900K vs $60K standard exemption.
- Requirement: Must file Form 706 disclosing worldwide assets.
2025 Long-term resident changes: Critical treaty protection
From 6 April 2025, the UK moved key inheritance tax concepts toward a residence-based test for non-UK assets. Individuals who are long-term UK residents can be within UK inheritance tax on worldwide assets, and a tail can apply after leaving. Treaty fiscal domicile can matter in cross-border cases.
What changed in 2025
The UK introduced a long-term UK resident concept for inheritance tax from 6 April 2025. Broadly, being a UK resident for 10 out of the previous 20 tax years can bring non-UK assets into scope, and leaving the UK can still leave a period of exposure depending on prior residence history.
Key changes (estate-focused):
- Long-term UK resident (LTR): UK resident for at least 10 of the previous 20 tax years.
- Worldwide UK IHT exposure: non-UK assets can be in scope while you are an LTR.
- Tail after leaving: the number of years before worldwide UK IHT switches off depends on how many UK-resident years you built up (ranging from 3 to 10 years under the statutory table).
- Trust impact: the excluded property concept for non-UK assets is now linked to whether the settlor is a long-term UK resident.
Treaty relief for long-term residents
The treaty can be relevant when UK domestic rules and treaty fiscal domicile point in different directions. In practice, executors may claim treaty relief by documenting treaty domicile and then applying the treaty’s taxing-rights and credit rules to limit overlap. This is fact-specific and documentation-heavy.
How this plays out in real life:
- UK rules may treat a former UK resident as still within worldwide UK IHT for a tail period.
- If the facts support US treaty domicile, the estate may have a stronger argument that certain non-UK assets should not be taxed as part of the UK worldwide charge (and any overlap should be relieved through credits).
Example (timeline):
A US citizen has lived in the UK for 22 years and returns to the US in 2026.
- UK law can keep worldwide IHT exposure for up to 10 years after leaving (depending on total resident years).
- If the estate can support US treaty domicile at death and claims treaty relief properly, the overall double-tax exposure can be reduced – particularly on non-UK assets during the tail period.
Treaty-protected trusts
The UK–US estate tax treaty includes a trust-specific rule that can preserve “excluded property” treatment for certain cross-border trusts. Where the settlor was US treaty domiciled and not a UK national when the trust was created, UK inheritance tax exposure can be restricted despite later UK residence.
New estate planning consideration:
- Pre-6 April 2025: Trusts created by non-UK domiciliaries could qualify as “excluded property,” keeping non-UK assets outside UK IHT.
- Post-6 April 2025 (LTR regime): Excluded property treatment can be lost if the settlor becomes a Long-term resident (LTR) under the 10-out-of-20-year test.
- Treaty protection: A trust created when the settlor was US treaty-domiciled and not a UK national may retain excluded property status under the estate and gift tax treaty.
- Critical requirement: Executors must prove the settlor’s US treaty domicile at the date the trust was settled.
Documentation tip: Keep the trust deed, nationality evidence, residence history, and domicile indicators. Treaty-protected trust claims are fact-sensitive and estate-specific.
Who benefits from the estate tax treaty
Anyone with assets in both countries facing estate or inheritance tax in both: US expats in the UK, UK nationals with US investments, long-term residents, and dual citizens exposed to cross-border double taxation.
US citizens in the UK (especially long-term residents)
- Benefit: Establish a US treaty domicile to avoid UK IHT on US assets and reduce double taxation exposure.
- LTR tail reduction: Potentially shorten a 10-year long-term resident tail to 3 years when returning to the US.
- Example: US citizen, UK resident, 18 years, $7M estate ($4M UK, $3M US). Treaty domicile can save $1.2M by excluding US assets from UK IHT.
UK nationals with US assets
- Benefit: Pro rata unified credit can increase the US exemption from $60K to $300K+ for US stocks or property.
- Example: UK resident, £10M estate including £2M US investments. Pro rata credit can save £780K in combined US estate tax and UK IHT.
Long-term residents planning to leave the UK
- Benefit: Treaty domicile may reduce the tail from 10 years to 3 years after departure.
- Saves: UK IHT on non-UK assets during years 4–10 post-departure.
- Critical for: US citizens returning to the US after 20+ years in the UK.
Practical calculation examples
Three scenarios demonstrate estate tax treaty savings using 2026 rates: US expat (LTR), UK national with US portfolio, dual citizen.
NOTE! Educational only. Cross-border estates depend on facts, valuations, elections, and correct treaty filings.
Example 1: US citizen, UK long-term resident
Sarah is a US citizen and a UK resident for 18 years. Her $7M estate includes $4M UK assets and $3M US assets. As a UK long-term resident, she falls within the worldwide UK inheritance tax without treaty coordination.
| Without treaty | With treaty |
|---|---|
| UK LTR → worldwide IHT | US treaty domicile applies |
| (£5.6M − £325K) × 40% = £2.11M ($2.64M) | UK taxes UK assets only |
| US estate tax: $0 (below exemption) | (£3.2M − £325K) × 40% = £1.15M ($1.44M) |
| Total ≈ $2.64M | Total ≈ $1.44M |
Savings: $2.64M − $1.44M = $1.2M saved via treaty domicile.
Example 2: UK national with US investments
James is UK-domiciled with a £12M estate: £10M UK assets and £2M US stocks (≈$2.5M). Without coordination, both the US estate tax and the UK IHT apply to the US-situs portion.
| Without treaty | With treaty |
|---|---|
| UK IHT: £4.67M | Pro rata credit formula applied |
| US estate tax: $976K (standard $60K exemption) | $13.99M × ($2.5M ÷ $15M) = $2.33M exemption |
| Combined ≈ £5.45M | US tax ≈ $760K |
| The UK allows credit for US tax paid | |
| Net ≈ £4.67M |
Savings: ≈ £780K through coordinated credit relief.
Example 3: Dual citizen
Maria is a dual US–UK citizen with a $5M estate ($2.5M in each country). Treaty domicile under the center of vital interests test points to the UK.
Result:
- UK taxes worldwide estate ≈ £4M → IHT ≈ £1.47M.
- US taxes US-situs assets only as non-domiciliary.
- Pro rata exemption covers $2.5M → $0 US estate tax.
Total ≈ £1.47M, rather than a stacked US + UK worldwide result.
How to claim estate tax treaty benefits
Treaty benefits under the UK–US inheritance tax treaty are claimed through estate tax filings – and the filings must match the treaty position.
In the US, the executor uses Form 706 (or Form 706-NA for nonresident estates) with treaty-relevant disclosures. In the UK, the executor uses IHT400 with treaty schedules (including IHT411).
US filing (Form 706 or Form 706-NA)
The US estate return depends on the decedent’s status. US citizens and domiciliaries generally use Form 706, while nonresident estates use Form 706-NA for US-situs assets. Treaty positions often require additional disclosure and careful schedule completion, including worldwide values where relevant.
Key filing points:
- Form 706: typically for US citizens/domiciliaries when the taxable estate exceeds the filing threshold for the year of death.
- Form 706-NA: typically for estates of nonresident not US citizens with US-situs assets.
- Treaty position: may involve a treaty disclosure (keep it brief here; do not duplicate the income treaty page).
- Deadline: commonly 9 months from the date of death (US extensions can be available).
UK filing (IHT400 + IHT411)
UK inheritance tax filings are generally made using IHT400, where an inheritance tax account is required. Treaty relief is commonly claimed through specific schedules, including IHT411 for double taxation convention relief. Executors should expect to provide evidence of foreign tax and the treaty basis.
Key filing points:
- IHT400: main account for chargeable estates.
- IHT411: schedule used to claim relief under double taxation conventions.
- Deadline: UK reporting and payment deadlines differ by case; executors should follow HMRC instructions and keep proof of foreign tax paid.
Essential documentation
Treaty claims live or die on evidence. Executors should collect a residence history, domicile indicators, asset location schedules, valuations at death, and proof of any foreign tax paid.
Trust documentation is crucial if treaty-protected trust rules may apply. Keep records long-term, not just until probate closes.
Documentation checklist:
- 10–20 year residence timeline (UK tax years matter)
- Proof of homes, family location, and long-term ties
- Asset register with situs (UK vs US) and valuations at death
- Foreign tax computations and receipts
- Trust deeds, letters of wishes, trustee minutes (if applicable)
Conclusion
The UK–US estate tax treaty and UK US inheritance tax treaty are separate from the income tax treaty and are designed to reduce double taxation on cross-border estates and gifts. With the UK’s 6 April 2025 long-term resident changes, understanding how the estate and gift tax treaty applies is now essential for many US expats in the UK and UK families with US assets.
Key points:
- The estate and gift tax treaty (separate from the income tax treaty) helps prevent double taxation on estates, gifts, and inheritances.
- Treaty domicile determines the primary taxing country. For domicile determination details, see the Income Tax Treaty guide.
- The pro rata unified credit can increase the US exemption from $60K to $300K+ for non-domiciliaries with US assets.
- The 2025 long-term resident changes make the treaty critical – in some cases, it can reduce a 10-year tail to 3 years.
- Executors claim treaty benefits through Form 706 (US) and IHT400 + Schedule IHT411 (UK).
Action: Document domicile status annually and ensure executors understand the treaty filing requirements before submitting returns.
FAQ
The treaty substantially reduces double taxation through treaty domicile rules and foreign tax credits. You may still owe tax in both countries, but Article 9 ensures you do not pay full estate or inheritance tax twice on the same assets.
They are separate treaties. The income tax treaty covers wages, dividends, pensions, and other income. The estate and gift tax treaty applies to estates, inheritances, and certain lifetime gifts, using different articles and relief mechanisms.
Yes. If you establish US treaty domicile, the UK 10-year long-term resident tail can be reduced to 3 years for individuals with 20+ years of UK residence. Executors must document US domicile factors and claim relief on IHT400.
Article 9A allows UK domiciliaries to claim a proportional US estate tax exemption based on worldwide assets. Example: $3M US assets in a $15M estate can produce a ~$2.8M exemption instead of the standard $60K. Requires full disclosure on Form 706.
Generally no. Estate tax treaty benefits are claimed after death by executors through Form 706 (US) and IHT400 (UK). Gift tax treaty provisions may apply during a lifetime for certain cross-border gifts.
Trusts created when the settlor was US treaty domiciled and not a UK national may remain outside UK inheritance tax, even if the settlor later becomes a long-term resident. Proof of domicile at the trust creation date is critical.
Article 4 applies the tie-breaker tests in sequence: permanent home, center of vital interests, habitual abode, and nationality. These rules determine which country has primary taxing rights for estate and gift tax purposes.
No. The treaty applies only to US federal estate and gift taxes and UK inheritance tax. US state-level estate or inheritance taxes (such as New York or Washington) are not covered.
Yes, if within statutory time limits. In the US, Form 706 amendments generally follow a 3-year limitation period. In the UK, IHT claims typically must be amended within 4 years of death. Interest or penalties may still apply.
If Article 4 tie-breakers do not resolve the issue, the competent authorities can use the mutual agreement procedure to determine a single treaty domicile. These cases are uncommon but can take 12–24 months to resolve.
