Inheritance Tax US UK Cross-Border Specialist Guide |

Introduction

You are part of a US-UK family — perhaps a US citizen married to a UK citizen, or a US-UK dual citizen with UK-based children, or a US citizen living in the UK with substantial assets on both sides of the Atlantic. Your worldwide net worth approaches or exceeds material US estate tax and UK Inheritance Tax thresholds. Your US estate planning attorney handles your US-side will, trust structures, and Form 706 framework — and your UK solicitor handles your UK-side will and UK IHT planning — but neither has substantive expertise on the integrated US-UK framework operating under the Estate Tax Treaty 1978. The US-UK cross-border inheritance tax specialist evaluation operates across both jurisdictions, requiring substantive, integrated coordination — most US-UK families operate suboptimal estate frameworks through generalist provider splits rather than integrated specialist coordination.

This guide is written for US-UK families with cross-border estate planning needs, US citizens domiciled in the UK with material worldwide assets, UK citizens domiciled in the US with material worldwide assets, US-UK dual citizens with assets in both jurisdictions, US citizens married to UK citizens with mixed-citizenship beneficiaries, and any US-UK family requiring specialist evaluation of integrated US estate tax and UK Inheritance Tax positioning. By the end, you will know exactly how the inheritance tax US UK cross-border specialist evaluation operates in 2026. For our broader US-UK service overview, see our US-UK cross-border tax advisory service.

What Is Inheritance Tax: US, UK, Cross-Border Specialist Evaluation

Inheritance tax US UK cross-border specialist evaluation refers to a comprehensive specialist analysis of the integrated US federal estate tax framework under Internal Revenue Code Sections 2001 through 2210 and the parallel UK Inheritance Tax framework under the Inheritance Tax Act 1984 for US-UK families with cross-border asset and beneficiary positioning, coordinated through the US-UK Estate Tax Convention of 1978 (the Estate Tax Treaty). The IRS estate tax reference sits at https://www.irs.gov/businesses/small-businesses-self-employed/estate-tax.

The US federal estate tax framework operates on US citizens and US tax domiciliaries on worldwide assets at progressive rates up to 40 percent under IRC Section 2001, with the lifetime exemption under IRC Section 2010 at approximately $7 million per person for 2026 (reduced from $13.99 million per person in 2025 following the TCJA sunset on 1 January 2026). Non-US-domiciled non-resident aliens are subject to US estate tax only on US situs assets, at the same progressive rates, but with a materially lower exemption ($60,000 under IRC Section 2102(b) absent treaty relief).

The UK Inheritance Tax framework operates under the Inheritance Tax Act 1984: for UK domiciliaries and UK deemed domiciliaries, on worldwide assets above the nil-rate band at 40 percent, and for non-UK domiciliaries, on UK situs assets only. The UK nil-rate band operates at £325,000 per person plus the Residence Nil-Rate Band of £175,000 per person, where qualifying conditions are met under IHTA 1984 sections 8A through 8M (the RNRB requires UK residential property passing to qualifying descendants with various restrictions for high-value estates above £2 million, tapering the RNRB).

The post-April 2025 UK domicile reforms under the Finance Act 2025 replaced the historic non-domicile framework with the Long-Term UK Resident (LTUKR) framework — UK IHT exposure on worldwide assets now applies to individuals who have been UK resident for at least 10 of the prior 20 UK tax years (replacing the historic 15-of-20-year deemed domicile rule under former ITA 2007 sections 835BA-835BD). The HMRC IHT reference sits at https://www.gov.uk/inheritance-tax.

The US-UK Estate Tax Convention of 1978 (the Estate Tax Treaty) coordinates the two frameworks through Article 4's domicile tiebreaker provisions, Article 5's situs rules, Articles 6 through 8's credit relief mechanisms, and other provisions that produce the substantive integrated framework. The Treaty operates as the central reference document for cross-border specialist coordination.

The professional credential framework underpinning inheritance tax US UK cross-border specialist evaluation typically includes UK Chartered Tax Adviser (CTA) credentialing under the Chartered Institute of Taxation with UK Trust and Estate specialism, UK STEP (Society of Trust and Estate Practitioners) membership supporting UK Trust and Estate planning, US Certified Public Accountant (CPA) or US IRS Enrolled Agent (EA) credentialing supporting US Form 706 estate tax preparation, US estate planning attorney coordination, and integrated cross-border specialist expertise across both jurisdictions simultaneously.

This matters in 2026 because the TCJA sunset on 1 January 2026 materially reduced the US lifetime exemption framework, the post-April 2025 UK domicile reforms under the Finance Act 2025 transformed the UK deemed domicile framework, and the 6 April 2027 UK pension fund inclusion in the UK IHT scope under the Finance Act 2025 creates new estate planning considerations. The September 2025 US-UK FATCA Intergovernmental Agreement data feed advances the IRS's automated detection of US-person UK financial holdings, affecting estate-planning visibility. The IRS reference sits at https://www.irs.gov/.

The real consequences of inadequate inheritance tax US UK cross-border specialist evaluation include US estate tax exposure under IRC Section 2001 up to 40 percent on worldwide assets above the reduced $7 million per person lifetime exemption, UK IHT exposure under IHT Act 1984 at 40 percent on worldwide assets above the £325,000 nil-rate band (plus £175,000 RNRB where qualifying) for UK domiciliaries and deemed domiciliaries or on UK situs assets for non-UK domiciliaries, double taxation exposure where both jurisdictions tax the same asset without proper Estate Tax Treaty 1978 coordination, missed lifetime gifting opportunities, missed trust structuring opportunities, and missed integrated US-UK estate planning frameworks.

Why Inheritance Tax US UK Cross-Border Specialist Evaluation Matters More Than Ever in 2026

The inheritance tax US UK cross-border specialist evaluation matters materially in 2026 for several distinct reasons. First, the TCJA sunset on 1 January 2026 reduced the US lifetime gift and estate exemption under IRC Section 2010 from $13.99 million per person (2025) to approximately $7 million per person (2026 indexed) — high-net-worth US-UK families face material new US estate tax exposure absent specific planning. The Treas Reg 20.2010-1(c) anti-clawback regulation preserves gifts made between 2018 and 2025 from clawback, but does not extend the higher exemption to gifts made in 2026.

Second, the post-April 2025 UK domicile reforms under the Finance Act 2025 transformed the UK deemed domicile framework. The historic 15-of-20-year deemed domicile rule under former ITA 2007 sections 835BA-835BD was replaced by the Long-Term UK Resident (LTUKR) framework, which requires UK residence for at least 10 of the prior 20 UK tax years — earlier UK IHT worldwide exposure for US-UK families with UK residence. You can read our broader guidance on our US-UK cross-border tax planning service.

Third, the 6 April 2027 UK pension fund inclusion in the UK Inheritance Tax scope under the Finance Act 2025 creates new estate planning considerations affecting UK workplace pensions and SIPPs held by US-UK families. UK pension funds will be included in the deceased's estate for UK IHT purposes, alongside other UK-situs assets, from 6 April 2027 — materially affecting US-UK families with substantial UK pension holdings.

Fourth, the integrated US estate tax and UK IHT framework under the Estate Tax Treaty 1978 is complex, requiring specialist coordination across both jurisdictions simultaneously — generalist US-only and UK-only estate planners typically lack the substantive, integrated cross-border depth. The IRS Treas Reg reference sits at https://www.irs.gov/.

Core Section: The Integrated US-UK Estate Tax Framework

US federal estate tax framework

The US federal estate tax framework is outlined in Internal Revenue Code Sections 2001 through 2210 and applies to US citizens and US tax domiciliaries on worldwide assets at progressive rates. The 2026 lifetime exemption under IRC Section 2010 operates at approximately $7 million per person following the TCJA sunset on 1 January 2026 — substantially reduced from the $13.99 million per person 2025 exemption.

The substantive estate tax computation operates on the gross estate (worldwide assets at fair market value at date of death) minus deductions (debts, funeral expenses, marital deduction under IRC Section 2056 with unlimited deduction for transfers to US-citizen spouses, charitable deduction under IRC Section 2055), equalling the taxable estate. The estate tax is computed on the taxable estate plus adjusted taxable gifts (lifetime gifts above the annual exclusion under IRC Section 2503) at progressive rates up to 40 percent, with the unified credit applied to absorb tax on the first $7 million per person of cumulative lifetime gifts and bequests.

For non-US-domiciled non-resident aliens, the US estate tax applies only to US situs assets under IRC Section 2103, with a materially lower exemption of $60,000 under IRC Section 2102(b), absent Estate Tax Treaty relief. The US-UK Estate Tax Treaty 1978, Article 6, increases the effective exemption for UK-domiciled non-resident aliens through proportional treatment based on the US situs assets-to-worldwide estate ratio.

US situs assets for non-resident aliens under IRC Section 2104 include US real estate, US tangible personal property located in the US, US corporate stock (shares of US corporations), US partnership interests where the partnership operates in the US, US-issued debt obligations of US persons (with portfolio interest exception under IRC Section 2105(b)), and other US-connected assets. Non-US situs assets include foreign real estate, foreign corporate stock, foreign partnership interests, US bank deposits (excluded under IRC Section 2105(b)), and life insurance proceeds on the decedent's life.

UK Inheritance Tax framework

The UK Inheritance Tax framework operates under the Inheritance Tax Act 1984 on UK domiciliaries and UK deemed domiciliaries (post-April 2025 Long-Term UK Resident framework) on worldwide assets at 40 percent above the nil-rate band, and on non-UK domiciliaries on UK situs assets only.

The UK nil-rate band under IHTA 1984 section 8 operates at £325,000 per person plus the Residence Nil-Rate Band of £175,000 per person under IHTA 1984 sections 8A through 8M, where qualifying conditions are met. The RNRB requires UK residential property passing to qualifying descendants (children, grandchildren, step-children, foster children) with various conditions. The RNRB tapers at £1 for every £2 of net estate above £2 million, producing a complete loss of RNRB at a net estate of £ 2.35 million per person.

The combined per-person UK IHT allowance for qualifying estates can reach £500,000 (£325,000 nil-rate band plus £175,000 RNRB) plus the transferable nil-rate band from a predeceased spouse where applicable, producing a potential combined £1 million UK IHT allowance for couples passing UK residential property to qualifying descendants. The HMRC IHT reference sits at https://www.gov.uk/inheritance-tax.

The post-April 2025 UK domicile reforms under the Finance Act 2025 replaced the historic non-domicile framework with the Long-Term UK Resident (LTUKR) framework. UK IHT exposure on worldwide assets now applies to LTUKR individuals — those who have been UK resident for at least 10 of the prior 20 UK tax years. The LTUKR framework operates as the substantive trigger for worldwide UK IHT exposure, replacing the historic 15-of-20-year deemed domicile rule.

UK situs assets for non-UK domiciliaries who are not LTUKR include UK real estate (UK residential and UK commercial property), UK tangible personal property located in the UK, UK corporate stock (shares of UK companies), UK partnership interests, UK government securities (UK gilts — with FOTRA exemption for non-UK-resident holders under FA 1996 section 154), UK bank deposits (with various exclusions and conditions), and other UK-connected assets.

US-UK Estate Tax Treaty 1978 coordination

The US-UK Estate Tax Convention of 1978 (the Estate Tax Treaty) coordinates the two frameworks. Article 4 establishes the domicile tiebreaker for individuals domiciled in both the US and UK under domestic law principles. Article 5 establishes situs rules for various asset categories, operating as supplementary to each jurisdiction's domestic situs rules. Articles 6 through 8 establish credit relief mechanisms that prevent double taxation through unilateral credit relief in the country with secondary taxing rights. The US Treasury treaty reference sits at https://home.treasury.gov/policy-issues/tax-policy/international-tax.

The substantive Treaty coordination produces the following framework for US-UK families. For a US-citizen US domiciliary who is also UK LTUKR (UK deemed domicile under the post-April 2025 framework), the Article 4 domicile tiebreaker typically establishes US domicile as the primary domicile, producing US estate tax on worldwide assets and UK IHT on UK situs assets only with the Treaty credit relief mechanism applying. For a UK-citizen UK-domiciliary who is also US-domiciled under IRC Section 2001(a), the Article 4 tiebreaker typically establishes UK domicile as the primary domicile, resulting in UK IHT on worldwide assets and US estate tax on US situs assets, with the Treaty credit relief mechanism applying.

For a US citizen, US domiciliary, married to a UK citizen, a UK domiciliary, the substantive framework is more complex. The US-citizen spouse benefits from the unlimited marital deduction under IRC Section 2056 for transfers to US-citizen spouses — but the marital deduction is unavailable for transfers from a US citizen to a non-US-citizen spouse (the surviving UK-citizen spouse) absent specific Qualified Domestic Trust (QDOT) structuring under IRC Section 2056A. The QDOT framework allows deferral of US estate tax on transfers from a US citizen decedent to a non-US citizen surviving spouse. Still, it requires specific trust structuring with a US trustee and various other conditions.

How US-UK Families Apply Inheritance Tax Cross-Border Specialist Engagement

The first step is the comprehensive US-UK family diagnostic. The specialist documents the family's US citizenship and US domicile positioning (US citizens by birth, naturalisation, derivative naturalisation; US tax domiciliaries under IRC Section 2001(a) substantial presence and intent tests), UK citizenship and UK domicile positioning (UK domicile of origin, UK domicile of choice, UK Long-Term UK Resident status under post-April 2025 framework), residency history in both jurisdictions, worldwide asset inventory with US situs and UK situs categorisation, beneficiary positioning across US-citizen and non-US-citizen family members, and integrated estate planning objectives.

The second step is the substantive analysis of the Estate Tax Treaty of 1978. The specialist applies the Article 4 domicile tiebreaker analysis where dual domicile applies, identifies the primary and secondary taxing rights jurisdictions, applies Article 5 situs rules to specific asset categories, projects the Articles 6 through 8 credit relief mechanisms preventing double taxation, and produces a preliminary integrated US-UK estate tax projection.

The third step is developing the lifetime gifting strategy. For US-citizen filers the substantive analysis evaluates lifetime gifting within the reduced $7 million per person 2026 lifetime exemption including annual exclusion gifts under IRC Section 2503(b) at $18,000 per donee per year (2025-26 indexed), 529 college savings plan contributions with 5-year forward annual exclusion election under IRC Section 529(c)(2)(B), direct medical and educational payments under IRC Section 2503(e), and substantive lifetime gifts using exemption. The IRS gift tax reference sits at https://www.irs.gov/businesses/small-businesses-self-employed/gift-tax.

The fourth step is the trust structuring evaluation. The substantive analysis evaluates various US-UK compatible trust structures, including Grantor Retained Annuity Trusts (GRATs) under IRC Section 2702, Intentionally Defective Grantor Trusts (IDGTs), Spousal Lifetime Access Trusts (SLATs), Qualified Personal Residence Trusts (QPRTs) under IRC Section 2702(a)(3)(B), and various UK trust structures operating under UK domestic law. Each structure has specific US- and UK-side tax consequences, requiring integrated specialist evaluation.

The fifth step is the post-April 2025 UK domicile and LTUKR positioning evaluation. For US-UK families with UK residence patterns, the specialist evaluates the timing of Long-Term UK Resident status, including the 10-of-prior-20-UK-tax-years test, the substantive implications of LTUKR status on worldwide UK IHT exposure, and potential planning approaches around LTUKR positioning (UK residence pattern management, asset positioning timing).

The sixth step is the 6 April 2027 UK pension IHT inclusion planning. UK workplace pensions and SIPPs held by US-UK families will be included in the deceased's UK IHT scope from 6 April 2027 onwards — the substantive analysis evaluates UK pension drawdown timing decisions, lifetime gifting from pension wealth where appropriate, integrated US-side Form 8833 treaty election under Article 18(5) considerations, and the integrated US-UK estate planning coordination.

The seventh step is the comprehensive integrated estate plan documentation. The specialist coordinates with a US estate planning attorney for US-side will and trust structures, a UK solicitor for UK-side will and trust structures, a US tax CPA for Form 706 framework preparation, a UK accountant for IHT400 framework preparation, and integrated US-UK estate plan documentation to ensure consistent treatment across all elements.

Real-World Example — Inheritance Tax US UK Cross-Border Specialist in Practice

Case Study: A US-UK Family With Substantial Combined Worldwide Assets Establishing an Integrated Estate Plan Under the Post-2026 Framework

Christopher and Anna are a US-UK family. Christopher is a US citizen (born and raised in the United States), aged 62, who has been residing in London with his family since 2018, having relocated from New York. Anna is a UK citizen (born and raised in the United Kingdom), aged fifty-nine, UK-domiciled by origin. They have three adult children — Emma (age 34, UK-resident UK citizen with her own UK family), Oliver (age 31, US-resident US-UK dual citizen working in San Francisco), and Sophie (age 28, UK-resident US-UK dual citizen working in London).

Christopher and Anna's combined worldwide net assets total approximately $24.5 million across US-domiciled assets ($8.2 million in US-domiciled investments including retained US brokerage accounts, US 401(k) and IRA accounts, US partnership interests, and US-domiciled life insurance), UK-domiciled assets ($14.8 million GBP-equivalent including UK principal residence in Kensington worth £4.8 million, UK investment portfolio worth £6.2 million across UK and non-UK equities, UK workplace pensions worth £1.4 million for Christopher and £0.8 million for Anna, UK SIPPs worth £0.6 million and £0.4 million respectively, and various other UK assets), and other non-US non-UK assets ($1.5 million in Singapore real estate from Christopher's pre-2018 Singapore residence period and Channel Islands-domiciled investment holdings).

In November 2025, Christopher and Anna engaged a US-UK Tax for a comprehensive cross-border inheritance tax specialist evaluation alongside their US estate planning attorney (US-based at a New York firm) and UK solicitor (UK-based at a London firm).

The US-UK Tax Diagnostic identified substantial considerations across the integrated framework. Christopher's US citizenship and continued US domicile (under IRC Section 2001(a) substantial intent test — Christopher maintained substantial US connections through US property, US brokerage accounts, US investment partnerships, and clear intent to return to the US in retirement) produced US estate tax on worldwide assets under IRC Section 2001 with the post-TCJA-sunset 2026 lifetime exemption of approximately $7 million per person. Anna's UK citizenship and UK domicile (UK domicile of origin, not displaced through UK domicile of choice considerations) produced UK IHT on worldwide assets under the IHT Act 1984.

Christopher's UK Long-Term UK Resident (LTUKR) status was evaluated under the post-April 2025 framework. Christopher had been a UK resident for the 2018-19 through 2024-25 UK tax years (seven UK tax years of UK residence) — not yet satisfying the 10-of-prior-20-UK-tax-years LTUKR test. Christopher would reach LTUKR status from the 2027-28 UK tax year onwards (the tenth UK tax year of UK residence, assuming continuous UK residence). The pre-LTUKR window (2025-26 through 2026-27 UK tax years) provided a substantive planning opportunity before Christopher's UK IHT exposure expanded from UK-situs assets only to worldwide assets.

The Article 4 Estate Tax Treaty 1978 domicile tiebreaker analysis confirmed Christopher's primary US domicile, resulting in US estate tax on worldwide assets and UK IHT on UK-situs assets only (subject to the LTUKR transition from the 2027-28 UK tax year). Anna's UK domicile produced UK IHT on worldwide assets and US estate tax on US situs assets only.

The integrated estate tax projection identified substantial exposure absent planning. Christopher's US estate tax projection at the reduced $7 million per person 2026 lifetime exemption produced approximately $7 million of taxable US estate (worldwide assets approximately $14 million attributable to Christopher minus $7 million exemption) at the 40 percent estate tax rate, producing approximately $2.8 million US estate tax exposure absent planning. Anna's UK IHT projection on UK worldwide assets approximately £8.5 million minus £325,000 nil-rate band minus potentially £175,000 RNRB (subject to qualification — the RNRB tapers above £2 million estate producing complete loss above £2.35 million producing zero RNRB for Anna's estate) producing approximately £8.175 million taxable UK estate at the 40 percent UK IHT rate producing approximately £3.27 million UK IHT exposure absent planning.

The integrated planning strategy was developed across multiple workstreams.

First, a lifetime gifting strategy. Christopher and Anna established annual exclusion gifts to the three children and their families at $18,000 per donee per year under IRC Section 2503(b) (Christopher) and £3,000 per donor per year under IHTA 1984 section 19 (Anna) producing combined annual exclusion gifting of approximately $108,000 plus £9,000 (across children and grandchildren where applicable) reducing both estates by approximately $135,000 USD-equivalent per year. Christopher executed a $4 million lifetime gift into a Spousal Lifetime Access Trust (SLAT) for Anna, using a substantial portion of his $7 million lifetime exemption, resulting in immediate US estate tax reduction. Anna executed a £2 million lifetime gift into a UK discretionary trust with a seven-year potentially exempt transfer (PET) framework under I, HTA 1984, section, resulting in an immediate UK estate reduction, subject to the seven-year survival rule.

Second, UK pension drawdown and integrated treatment planning. The 6 April 2027 UK pension fund inclusion in the UK IHT scope created urgency for pre-2027 UK pension drawdown planning. Christopher's £1.4 million UK workplace pension and £0.6 million SIPP were evaluated for pre-2027 drawdown timing with integrated US-side Form 8833 treaty election under Article 18(5) considerations and Form 1116 Foreign Tax Credit positioning on UK Income Tax paid on pension drawdowns. Anna's £0.8 million UK workplace pension and £0.4 million SIPP were similarly evaluated. The pre-2027 drawdown strategy was integrated with lifetime gifting from drawn pension proceeds into UK discretionary trusts with a seven-year PET framework.

Third, US-UK trust structuring. Christopher's lifetime gift into the SLAT for Anna's benefit operated as a Grantor Trust for US income tax purposes, resulting in continued US income tax responsibility for Christopher on trust income (preserving the "income tax burn" arrangement and strengthening estate reduction) while removing trust assets from Christopher's US gross estate. Anna's lifetime gift to the UK discretionary trust operated as a UK discretionary trust with a seven-year PET framework requiring Anna to survive seven years from the gift date for the gifted assets to fall outside her UK IHT estate.

Fourth, US-UK property positioning. The UK principal residence in Kensington, valued at £4.8 million, was evaluated for UK IHT purposes. The £175,000 RNRB tapered to zero given the high net estate value (above £2.35 million per person), resulting ing in no RNRB available. The integrated planning evaluated lifetime restructuring through joint tenancy positioning, fractional gifting, or potential trust structuring — with substantive analysis indicating that joint tenancy with Anna produces the optimal positioning under the UK marital deduction framework, along with the integrated US-side analysis.

Fifth, integrated US-side documentation. The US estate planning attorney coordinated US will updates, US Spousal Lifetime Access Trust documentation, US Grantor Trust positioning, IRC Section 2056 marital deduction analysis (Anna is non-US-citizen producing absence of unlimited marital deduction — Qualified Domestic Trust (QDOT) framework under IRC Section 2056A was evaluated and structured for residual US estate transfers to Anna at Christopher's death), and Form 706 framework for projected eventual filing.

Sixth, integrated UK-side documentation. The UK solicitor coordinated UK updates, UK discretionary trust documentation, UK seven-year PET tracking, UK IHT400 framework for projected eventual filing, and integrated UK lifetime gifting documentation.

Seventh, ongoing integrated annual review. The integrated US-UK annual workflow established annual review meetings covering progress on the lifetime gifting strategy (annual exclusion gifts continuing), the seven-year PET tracking for Anna's lifetime gifts, the Christopher LTUKR transition timing (2027-28 UK tax year), the 6 April 2027 UK pension IHT inclusion implementation, integrated US-side Form 1040 and Form 8833 treaty election continuation, and any adjustment to the integrated estate plan based on changing circumstances.

The total US-UK Tax engagement scope covered comprehensive inheritance S-UK, the comprehensive inheritance cross-border specialist evaluation, and the integrated estate plan establishment, at approximately £58,000 fixed fee (with coordination overhead with the US estate planning attorney, and additional New York firm fees,s and the UK solicitor at additional London firm fees). The going-forward annual integrated workflow operated at approximately £28,500, coveringcomprehensive ongoing integrated US-UK estate plan management.

The outcome was a comprehensive integrated US-UK estate plan reducing combined projected estate tax exposure from approximately $2.8 million US plus £3.27 million UK (approximately $6.9 million USD-equivalent total exposure absent planning) to approximately $1.2 million US plus £1.85 million UK (approximately $3.7 million USD-equivalent total exposure post-planning) — combined estate tax saving of approximately $3.2 million USD-equivalent. The case study illustrates the inheritance tax US UK cross-border specialist evaluation in practical operation — the integrated framework across US estate tax, UK Inheritance Tax, US-UK Estate Tax Treaty 1978 coordination, lifetime gifting strategy, US-UK trust structuring, UK LTUKR transition planning, 6 April 2027 UK pension IHT inclusion planning, and US-UK Qualified Domestic Trust framework requires substantive specialist coordination across both jurisdictions simultaneously.

Common Mistakes People Make With Inheritance Tax: US, UK, Cross-Border Specialist Evaluation

The first mistake is assuming the US-UK Estate Tax Treaty of 1978 eliminates double taxation. The Treaty coordinates the two frameworks and provides credit relief mechanisms to prevent technical double taxation, but does not eliminate the underlying US estate tax and UK IHT exposure — the integrated framework produces material combined exposure for US-UK families absent specific planning. The US Treasury treaty reference sits at https://home.treasury.gov/policy-issues/tax-policy/international-tax.

The second mistake is failing to evaluate the post-April 2025 UK Long-Term UK Resident (LTUKR) framework for US citizens resident in the UK. The LTUKR framework under the Finance Act 2025 replaced the historic 15-of-20-year deemed domicile rule with the 10-of-prior-20-UK-tax-years test — US citizens with UK residence approaching the LTUKR threshold face material new UK IHT exposure on worldwide assets, requiring pre-LTUKR planning and execution.

The third mistake is failing to plan for the 6 April 2027 UK pension fund inclusion in the scope of UK Inheritance Tax. UK workplace pensions and SIPPs held by US-UK families will be included in the deceased's UK IHT estate from 6 April 2027 onwards — material new UK IHT exposure on UK pension wealth requiring pre-2027 planning, including potential pension drawdown timing decisions, lifetime gifting from pension wealth, and integrated US-side Form 8833 treaty election continuation considerations. The HMRC reference sits at https://www.gov.uk/.

The fourth mistake is failing to apply the US Qualified Domestic Trust (QDOT) framework under IRC Section 2056A for transfers from US-citizen decedents to non-US-citizen surviving spouses. The unlimited marital deduction under IRC Section 2056 is unavailable for transfers to non-US-citizen spouses absent specific QDOT structuring with a US trustee and various other conditions — US-UK families with US-citizen / non-US-citizen spouse positioning face material US estate tax exposure absent QDOT planning at the US-citizen decedent's death.

The fifth mistake is failing to execute lifetime gifting before the TCJA sunset reduced the US lifetime exemption from $13.99 million per person (2025) to approximately $7 million per person (2026 indexed). The 2025 planning window for high-value lifetime gifts using the higher exemption has closed — but ongoing lifetime gifting within the reduced $7 million per person framework remains substantively valuable for high-net-worth US-UK families. The IRS reference sits at https://www.irs.gov/.

The sixth mistake is engaging US-only estate planners or UK-only estate planners for cross-border US-UK family work. The integrated US-UK estate tax framework requires substantive specialist depth in both jurisdictions simultaneously, plus coordination through the Estate Tax Treaty 1978 — generalist US-only and UK-only estate planners typically lack the integrated cross-border depth required for substantive US-UK estate planning, resulting in missed planning opportunities.

How US-UK Tax Can Help You With Inheritance Tax: US-UK Cross-Border Specialist Evaluation

US-UK Tax is a specialist US-UK cross-border advisory firm with comprehensive expertise on the integrated US estate tax and UK Inheritance Tax framework operating under the US-UK Estate Tax Convention of 1978. Our team holds UK Chartered Tax Adviser (CTA) credentials under the Chartered Institute of Taxation with UK Trust and Estate specialism, UK STEP (Society of Trust and Estate Practitioners) membership where applicable, US IRS Enrolled Agent (EA) credentials supporting substantive US Form 706 estate tax framework preparation and IRS representation, US-UK estate planning coordination expertise, and integrated cross-border specialist expertise across both jurisdictions simultaneously. The CIOT reference sits at https://www.tax.org.uk/, and the STEP reference sits at https://www.step.org/.

For US-UK family clients we deliver comprehensive inheritance tax US UK cross-border specialist evaluation and integrated estate planning engagement including US citizenship and US domicile diagnostic under IRC Section 2001(a), UK citizenship and UK domicile diagnostic under common law and post-April 2025 Long-Term UK Resident framework, US-UK Estate Tax Treaty 1978 Article 4 domicile tiebreaker analysis, Article 5 situs rules application, Articles 6-8 credit relief mechanism analysis, lifetime gifting strategy development including annual exclusion gifts under IRC Section 2503(b) and IHTA 1984 section 19 framework plus substantive lifetime exemption gifting under reduced post-TCJA $7M per person framework plus UK seven-year PET framework under IHTA 1984 section 3A, US-UK trust structuring including Spousal Lifetime Access Trusts (SLATs), Intentionally Defective Grantor Trusts (IDGTs), Qualified Personal Residence Trusts (QPRTs), Grantor Retained Annuity Trusts (GRATs) under IRC Section 2702, UK discretionary trusts, and UK life interest trusts, Qualified Domestic Trust (QDOT) framework under IRC Section 2056A for transfers to non-US-citizen surviving spouses, post-April 2025 UK Long-Term UK Resident framework planning, 6 April 2027 UK pension fund IHT inclusion planning including UK pension drawdown timing decisions and integrated US-side Form 8833 treaty election continuation under Article 18(5), Form 706 framework preparation coordination, IHT400 framework preparation coordination, integrated US estate planning attorney and UK solicitor coordination, and ongoing integrated US-UK annual workflow coordination. You can read our broader guidance on our US-UK cross-border tax advisory service.

Standard integrated US-UK inheritance tax; US-UK cross-border specialist engagement fees vary by complexity. Initial diagnostic and integrated estate plan development typically costs £15,000 to £85,000+, depending on substantive scope and complexity (worldwide asset value, family composition, citizenship and domicile complexity, trust structuring requirements, UK LTUKR transition planning, UK pension IHT inclusion planning). Going forward, annual integrated workflow fees range from £8,500 to £55,000+, depending on complexity. Get in touch with our team today at or visit https://www.us-uktax.com/ to discuss your situation.

Conclusion

Three takeaways matter most for US-UK families evaluating inheritance tax, US-UK cross-border specialist positioning in 2026. First, the integrated US estate tax and UK Inheritance Tax framework operates across two parallel transfer tax systems coordinated through the US-UK Estate Tax Convention of 1978 — US federal estate tax under IRC Sections 2001 through 2210 with the post-TCJA-sunset 2026 lifetime exemption of approximately $7 million per person (reduced from $13.99 million per person in 2025) at progressive rates up to 40 percent and UK Inheritance Tax under IHT Act 1984 with the £325,000 nil-rate band plus £175,000 Residence Nil-Rate Band per person where qualifying at 40 percent above the bands. Second, the post-April 2025 UK Long-Term UK Resident (LTUKR) framework under Finance Act 2025 (replacing the historic 15-of-20-year deemed domicile rule with the 10-of-prior-20-UK-tax-years test), the 6 April 2027 UK pension fund inclusion in UK Inheritance Tax scope under Finance Act 2025, the TCJA sunset on 1 January 2026 reducing the US lifetime exemption, and the integrated Estate Tax Treaty 1978 coordination together produce a materially transformed planning environment for US-UK families requiring substantive specialist re-evaluation. Third, the integrated US-UK estate planning requires comprehensive specialist coordination across both jurisdictions simultaneously including lifetime gifting strategy under both reduced US lifetime exemption and UK seven-year PET framework, US-UK compatible trust structuring (SLATs, IDGTs, QPRTs, UK discretionary trusts), Qualified Domestic Trust (QDOT) framework under IRC Section 2056A for transfers to non-US-citizen surviving spouses, integrated US estate planning attorney and UK solicitor coordination, and ongoing integrated annual workflow management. Speak to a US-UK Tax adviser today — contact us at or visit https://www.us-uktax.com/.

Frequently Asked Questions About Inheritance Tax US UK Cross-Border Specialist

Q: Do US citizens have to pay both the US estate tax and the UK Inheritance Tax?

A: Potentially yes, depending on the specific US-UK family circumstances. US citizens are subject to US federal estate tax on worldwide assets under IRC Section 2001 with the post-TCJA-sunset 2026 lifetime exemption of approximately $7 million per person. UK domiciliaries and Long-Term UK Residents (post-April 2025 framework) are subject to UK Inheritance Tax on worldwide assets under the IHT Act 1984, with a £325,000 nil-rate band per person. US-UK families with dual exposure are coordinated through the US-UK Estate Tax Convention of 1978, with Article 4's domicile tiebreaker establishing primary taxing rights and Articles 6 through 8 providing credit relief mechanisms to prevent technical double taxation—but the integrated framework still produces material combined exposure for many US-UK families, requiring specialist planning. The IRS reference sits at https://www.irs.gov/.

Q: What is the US-UK Estate Tax Treaty, and how does it work?

A: The US-UK Estate Tax Convention of 1978 (commonly called the US-UK Estate Tax Treaty) is the bilateral treaty coordinating US federal estate tax and UK Inheritance Tax for individuals with dual US-UK exposure. Article 4 establishes the domicile tiebreaker for individuals domiciled in both jurisdictions under domestic law principles. Article 5 establishes situs rules for various asset categories operating as supplementary to domestic situs rules. Articles 6 through 8 establish credit relief mechanisms that prevent technical double taxation by providing unilateral credit relief in the country of secondary taxing rights. The Treaty does not eliminate the underlying combined exposure — it coordinates the two frameworks to prevent technical double taxation. The US Treasury treaty reference sits at https://home.treasury.gov/policy-issues/tax-policy/international-tax.

Q: How does the TCJA sunset affect my US-UK estate planning?

A: The TCJA sunset on 1 January 2026 reduced the US lifetime gift and estate exemption under IRC Section 2010 from $13.99 million per person (2025) to approximately $7 million per person (2026 indexed). For high-net-worth US-UK families, the reduced exemption substantially increases US estate tax exposure absent specific planning. The Treas Reg 20.2010-1(c) anti-clawback regulation preserves gifts made between 2018 and 2025 from clawback but does not extend the higher exemption to gifts made in 2026. US-UK families approaching or exceeding the reduced $7 million per person threshold face heightened planning urgency, including potential lifetime gifting within the reduced exemption, US-UK-compatible trust structuring, and integrated UK-side coordination.

Q: What is the Long-Term UK Resident (LTUKR) framework, and how does it affect US citizens in the UK?

A: The Long-Term UK Resident (LTUKR) framework under Finance Act 2025 replaced the historic UK 15-of-20-year deemed domicile rule under former ITA 2007 sections 835BA-835BD from 6 April 2025 onwards. LTUKR status applies to individuals who have been UK resident for at least 10 of the prior 20 UK tax years — substantially earlier than the historic 15-of-20-year framework. LTUKR status results in UK Inheritance Tax exposure for worldwide assets (rather than only UK-situs assets) regardless of UK common law domicile status. For US citizens resident in the UK approaching the 10-year UK residence threshold, the LTUKR transition planning is materially important — pre-LTUKR planning windows allow lifetime gifting and asset positioning before the worldwide UK IHT exposure triggers. The HMRC reference sits at https://www.gov.uk/.

Q: How does the 6 April 2027 UK pension IHT inclusion affect my US-UK estate plan?

A: The Finance Act 2025 announced the inclusion of UK pension funds (UK workplace pensions and SIPPs) in the UK Inheritance Tax scope from 6 April 2027 — UK pension funds will be included in the deceased's estate for UK IHT purposes alongside other UK assets. For US-UK families with material UK pension holdings, the 2027 change creates new estate planning considerations, including potential pre-2027 UK pension drawdown timing decisions, lifetime gifting from drawn pension wealth where appropriate, integrated US-side Form 8833 treaty election continuation under Article 18(5), and Form 1116 Foreign Tax Credit positioning on UK Income Tax paid on UK pension drawdowns. Specialist evaluation of the integrated US-UK pension and estate framework before 6 April 2027 is of material importance.

Q: Can I use a Qualified Domestic Trust (QDOT) for transfers to my non-US-citizen UK spouse?

A: Yes. The Qualified Domestic Trust (QDOT) framework under IRC Section 2056A allows US-citizen decedents to defer US federal estate tax on transfers to non-US-citizen surviving spouses by leaving the property to a QDOT rather than directly to the non-US-citizen surviving spouse. The unlimited marital deduction under IRC Section 2056 is unavailable for direct transfers to non-US citizen spouses unless a QDOT structure is used. The QDOT requires specific conditions, including a US trustee (at least one US-citizen trustee or a US-domestic corporation trustee), withholding of US estate tax on principal distributions, US estate tax assessment on the remaining trust principal at the surviving spouse's death, and various other conditions. The QDOT framework is substantively important for US-citizen / non-US-citizen spouse US-UK families. The IRS reference for QDOT sits at https://www.irs.gov/.

Q: What lifetime gifting strategies work for US-UK families?

A: Multiple parallel frameworks operate. On the US side annual exclusion gifts under IRC Section 2503(b) at $18,000 per donee per year (2025-26 indexed) can be made without using the lifetime exemption — combined with educational and medical payments under IRC Section 2503(e) and 529 college savings plan contributions with 5-year forward annual exclusion election under IRC Section 529(c)(2)(B). Substantive lifetime gifts above the annual exclusion use the post-TCJA $7 million per person 2026 lifetime exemption under IRC Section 2010. On the UK side, annual exclusion gifts under IHTA 1984 section 19 at £3,000 per donor per year (with one-year carryover for unused exemption) operate, plus the small gifts exemption under IHTA 1984 section 20 at £250 per donor per year, plus the wedding gift exemption under IHTA 1984 section 22, plus the normal expenditure out of income exemption under IHTA 1984 section 21. Substantive UK lifetime gifts are subject to the seven-year potentially exempt transfer (PET) framework under IHTA 1984, section 3A. If the gift survives for seven years from the gift date, the gifted assets are removed from the donor's UK IHT estate. An integrated US-UK lifetime gifting strategy requires simultaneous coordination across both frameworks.

Q: Can US-UK Tax help me with my US-UK estate planning?

A: Yes. Our standard integrated US-UK inheritance tax US UK cross-border specialist engagement covers comprehensive US citizenship and US domicile diagnostic, UK citizenship and UK domicile diagnostic including post-April 2025 LTUKR framework analysis, US-UK Estate Tax Treaty 1978 Article 4 domicile tiebreaker analysis with Article 5 situs rules and Articles 6-8 credit relief mechanisms, lifetime gifting strategy development across both US annual exclusion and lifetime exemption framework and UK annual exclusion and seven-year PET framework, US-UK compatible trust structuring including Spousal Lifetime Access Trusts (SLATs), Intentionally Defective Grantor Trusts (IDGTs), Qualified Personal Residence Trusts (QPRTs), Grantor Retained Annuity Trusts (GRATs), UK discretionary trusts, and UK life interest trusts, Qualified Domestic Trust (QDOT) framework under IRC Section 2056A for transfers to non-US-citizen surviving spouses, post-April 2025 UK Long-Term UK Resident framework planning, 6 April 2027 UK pension fund IHT inclusion planning, Form 706 framework preparation coordination, IHT400 framework preparation coordination, integrated US estate planning attorney and UK solicitor coordination, and ongoing integrated US-UK annual workflow coordination. Initial diagnostic and integrated estate plan development engagement fees typically range from £15,000 to £85,000+, depending on complexity, with ongoing annual integrated workflow fees ranging from £8,500 to £55,000+. Contact to discuss your situation.