Estate Planning Across Multiple Jurisdictions: A Guide for International Families

Families with assets, residences, or members spread across multiple countries face some of the most complex estate planning challenges in wealth management. The interaction of different countries' succession laws, tax rules, and conflict-of-law principles can produce results that bear no resemblance to what a person intended — or impose tax liabilities in multiple countries on the same assets. Understanding the international framework, and taking co-ordinated advice in each relevant jurisdiction, is essential to achieving an effective and enforceable estate plan.

The Foundational Concepts: Domicile vs Habitual Residence

Domicile is the concept that most directly determines which country's succession law applies to movable assets (shares, cash, personal property) under English conflict-of-law rules. Domicile is a complex concept — broadly, it refers to the country a person regards as their permanent home and intends to return to indefinitely. It is distinct from nationality, residence, and tax residence. A person can be resident in the UK for tax purposes while remaining domiciled in Australia, for example.

For UK inheritance tax purposes, UK-domiciled individuals (and, since the 2025 reforms, long-term UK residents) are taxed on their worldwide assets. Non-UK domiciliaries are taxed only on UK-situated assets.

Habitual residence is the concept used in EU private international law to determine applicable law in succession matters. Broadly, it refers to the country where a person is regularly and habitually present, with a degree of stability and intention to continue living there. Habitual residence is typically easier to establish and change than domicile.

EU Succession Regulation (Brussels IV)

The EU Succession Regulation (Regulation 650/2012, known as "Brussels IV"), which came into force on 17 August 2015, harmonised succession law across most EU member states (Denmark and Ireland did not opt in). Its key provisions:

• General rule: the law applicable to the succession of a deceased's estate is the law of the country where the deceased was habitually resident at the date of death.
• Choice of law: a person can choose the law of their nationality to apply to their entire estate (by making a declaration in their Will).
• EU cross-border recognition: judgments and authentic instruments relating to succession made in one EU member state are recognised across the EU.

The regulation covers succession law (who inherits what) rather than tax — inheritance tax remains subject to each country's national rules and any applicable bilateral treaties.

Impact of Brexit. The UK was subject to Brussels IV while an EU member but chose not to opt in. Post-Brexit, the UK no longer participates in Brussels IV. For UK nationals with assets in EU countries, Brussels IV still applies to those EU-situated assets, but the UK will not automatically apply Brussels IV rules to UK assets. This creates potential for jurisdictional conflict — a topic that requires careful Will drafting and, often, advice from lawyers qualified in both the UK and the relevant EU jurisdiction.

UK-Spain Estate Planning

Spain is a particularly complex jurisdiction for UK nationals, as many British retirees and second-home owners have significant assets there.

Spanish succession law. Spain's Civil Code imposes "forced heirship" rules: certain portions of the estate (the "legítima") must pass to direct descendants. The share reserved for forced heirs depends on whether there are children, grandchildren, or other relatives. A UK national can elect, under Brussels IV (which still applies to their Spanish assets as an EU member state rule), to have UK law govern succession to their Spanish estate — potentially enabling them to override Spanish forced heirship with the freedom of disposition available under English law.

Spanish inheritance tax (IHT). Spain imposes its own inheritance tax on Spanish-situated assets. There are allowances for close relatives and for Spanish residents, but non-residents may face higher rates. Double tax treaty relief is limited (the UK-Spain double tax treaty does not cover inheritance tax comprehensively). However, Spanish regional governments have significant devolved powers over inheritance tax, and the rules in Andalucía, Madrid, and Catalonia vary materially.

UK-France Estate Planning

France is similarly complex, with a combination of forced heirship rules and a French inheritance tax system.

French succession law. France also applies forced heirship (réserve héréditaire). The forced share for a single child is 50%; for two children, 66%; for three or more, 75%. Unlike Spain, France does not allow non-EU citizens to elect UK law under Brussels IV (as the UK is no longer an EU state). However, French courts have generally permitted the application of UK law to movable assets of UK-domiciled individuals under pre-existing French conflict-of-law rules, though this area is evolving.

French succession tax. French succession tax applies to French-situated property and, in some circumstances, to assets passed to French-resident beneficiaries. A bilateral UK-France succession tax convention exists, providing some relief from double taxation, but coordination is complex. The convention applies to estates of UK-domiciled individuals; its interaction with the post-2025 non-dom rules requires specialist advice.

US-UK Estate Planning

US-UK estate planning is among the most complex in international private client practice. The combination of:

• US estate tax applying to worldwide assets of US citizens and long-term green card holders, wherever resident.
• UK inheritance tax applying to worldwide assets of UK-domiciled individuals.
• A bilateral US-UK estate and gift tax treaty (signed 1978, in force from 1979) that provides relief from double taxation.

...creates a layered framework that requires co-ordinated advice from lawyers and tax advisers qualified in both jurisdictions.

Key issues in US-UK estate planning:

US persons. US citizens — including those living permanently in the UK — are subject to US federal estate tax on their worldwide assets. The current federal estate tax exemption ($15m per person for 2026, made permanent and index-linked by the One Big Beautiful Bill Act of 2025) provides significant relief, but the interaction with UK IHT means that large estates may face IHT on the UK end and estate tax on the US end, even after treaty relief.

Non-citizen spouses. The US unlimited spousal exemption (which exempts all assets passing to a US citizen spouse) does not apply to assets passing to a non-citizen spouse. Assets must be held in a Qualified Domestic Trust (QDOT) to access a form of deferred US estate tax treatment.

UK-resident, non-UK-domiciled US citizens. These individuals face US estate tax on worldwide assets and UK IHT only on UK-sited assets — potentially a favourable position, but one that requires careful structuring.

Jurisdictional Conflict Resolution

Conflicting claims between jurisdictions — where two countries both assert the right to tax or govern a succession — are resolved through:

• Bilateral tax treaties. The UK has bilateral treaties covering estate/succession taxes with a limited number of countries (the US, France, Ireland, India, South Africa, Sweden, and a few others). Where a treaty exists, it determines which country has primary taxing rights on different categories of asset.
• Unilateral relief. Where no treaty exists, the UK provides unilateral double tax relief allowing a credit for overseas succession taxes paid against the UK IHT liability on the same asset.
• Choice of law provisions. Including jurisdiction-of-choice clauses in Wills and trust deeds, making declarations under Brussels IV where available, and seeking advance rulings from tax authorities where possible.

When conflicts arise between succession laws (rather than tax), the position is more difficult. Forced heirship claims from EU jurisdictions may be enforceable against EU-situated assets even where a UK Will directs them elsewhere.

Single Will vs Multiple Wills

For individuals with assets in multiple jurisdictions, the choice between a single worldwide Will and separate jurisdiction-specific Wills is a fundamental planning decision.

Single worldwide Will. A single Will drafted under English law can be expressed to apply to worldwide assets. This is administratively simpler but may not be recognised, or may be difficult to administer, in some foreign jurisdictions. Probate in a foreign jurisdiction is often required for local assets even where a foreign Will exists.

Multiple Wills. Separate Wills for each jurisdiction in which significant assets are held — drafted by local lawyers to comply with local formalities and succession law — can reduce delays and costs in the administration process. However, multiple Wills must be carefully co-ordinated to ensure they do not inadvertently revoke each other, and they must be consistent in their overall distribution scheme.

The Hague Convention on the Conflicts of Laws Relating to the Form of Testamentary Dispositions (implemented in the UK by the Wills Act 1963) provides a broad range of connecting factors under which a Will may be formally valid — making a UK Will formally valid in many countries even without a local Will.

Practical Steps

For internationally mobile individuals:

1. Identify all jurisdictions in which you hold assets or are habitually resident.
2. Obtain advice from lawyers qualified in each relevant jurisdiction.
3. Co-ordinate Will drafting across jurisdictions to ensure consistency and to avoid inadvertent revocation.
4. Review choice of law options under Brussels IV (for EU-situated assets) and bilateral treaties.
5. Review the IHT and succession tax position in each jurisdiction and ensure double tax relief is claimed where available.
6. Review any forced heirship exposures and assess whether choice of law elections or trust structures can mitigate them.
7. Keep Wills and estate plans under review as residence, domicile, assets, and family circumstances change.

How Global Investments Can Help

Global Investments co-ordinates international estate planning for clients with assets and family connections across multiple jurisdictions. We work closely with specialist private client solicitors in the UK and our network of international advisers to help you build a comprehensive, consistent, and enforceable estate plan across all relevant jurisdictions. Contact us to discuss your cross-border estate planning needs.

This guide is for information purposes only and does not constitute legal, tax, or estate planning advice. International succession planning is highly complex and fact-specific. Readers must obtain independent professional legal advice in each relevant jurisdiction. Rules and treaties cited are as at June 2026 and are subject to change.