Cross-Border Families

What Makes a Family "Cross-Border"

The term covers a wide range of situations. A family might be cross-border because two spouses hold different citizenships, because adult children relocated to work in another country, because aging parents retired abroad, or because a business sale left one generation flush with assets parked in a foreign trust or holding company. Sometimes a family becomes cross-border gradually — one child takes a job in Europe, another marries someone from Asia — without anyone sitting down to evaluate what that means legally.

The shared feature in every case is that more than one country's legal system asserts some authority over the family. That authority may relate to income taxes, estate and gift taxes, marital property, inheritance rights, or all of the above. For context on how wealth complexity escalates across wealth levels, see Global Wealth and Managing Substantial Wealth.

Residency, Domicile, and Why They Differ

Residency typically refers to a legal status — often tied to how many days per year a person physically spends in a country. Domicile is a deeper concept: the country (or state) a person treats as their permanent home and intends to return to. A person can be a tax resident of one country while domiciled in another, and the two countries may draw different conclusions about which of them has primary taxing authority.

This matters enormously for estate planning. Many civil-law countries tax an estate based on where the deceased was domiciled; others tax based on where the assets are located; a few claim authority on both grounds. A U.S. citizen living in France, for example, may find both countries asserting rights over the same estate — a classic source of double taxation.

Treaty tie-breakers are provisions in bilateral tax treaties that establish which country "wins" when both claim residency or domicile. Not every pair of countries has such a treaty, and the treaties that exist do not always cover gift or estate taxes. Families should never assume that a treaty eliminates the problem — a qualified attorney familiar with both jurisdictions must evaluate the specific facts.

Marital Property Regimes in Conflict

Countries differ sharply in how they define ownership of assets acquired during a marriage. Common-law countries (such as the United States and the United Kingdom) generally treat each spouse as the owner of whatever they earned or received, subject to equitable division on divorce. Civil-law countries (including most of continental Europe and Latin America) often apply a community property regime by default, meaning assets acquired during the marriage are automatically co-owned, regardless of which spouse's name is on the title.

When spouses come from different legal traditions, or when a couple moves from one country to another, their marital property regime may be disputed. Consider a hypothetical: a German spouse and a U.S. spouse marry, live in Germany for twenty years, then move to the United States. Depending on which country's rules apply, the division of assets on divorce or death could look very different. A prenuptial agreement drafted with cross-border enforceability in mind is often one of the first tools families in this situation explore — but an attorney licensed in each relevant jurisdiction must evaluate whether and how such an agreement holds up.

Forced Heirship vs. Testamentary Freedom

Forced heirship is the rule, common in civil-law countries and some Islamic legal systems, that reserves a mandatory portion of an estate for specific family members — typically children and sometimes a surviving spouse — regardless of what the deceased's will says. The concept is largely foreign to common-law countries, where testamentary freedom allows a person to leave assets to whomever they choose.

For a cross-border family, this conflict can be severe. A U.S.-based parent who wishes to leave the bulk of an estate to charity may be legally prohibited from doing so under the laws of a country where a child resides or holds citizenship. Conversely, a child in a common-law country may be surprised to discover that assets their parent held in a civil-law country are subject to forced-heirship claims they never anticipated.

Some countries allow individuals to elect which country's succession law governs their estate — a flexibility introduced in part by the European Union's Succession Regulation. Whether such an election is available, and how it interacts with other countries' rules, is a question for specialized legal counsel. For a broader introduction to estate-planning structure, see Estate Planning: The Landscape.

Overlapping Tax Obligations

Tax complexity is often the most immediately pressing concern. A family member who is both a U.S. citizen and a resident of another country typically owes U.S. tax on worldwide income regardless of where they live — a feature of U.S. tax law that is unusual among developed nations. At the same time, their country of residence may also tax their worldwide income. Foreign tax credits can reduce but not always eliminate double taxation, and the mechanics differ by treaty, by asset type, and by the structure through which income flows.

Gifts and inheritances add another layer. The estate and gift tax system in the United States applies to U.S. citizens and certain residents on a worldwide basis, while many other countries impose inheritance taxes on the recipient rather than the estate. The same transfer may be taxed twice under two different legal theories. For families navigating these filing obligations, International Reporting Regimes provides a useful reference on disclosure requirements such as FBAR and FATCA, and Expatriation covers the considerations that arise when someone considers giving up citizenship or long-term residency entirely.

The Coordination Pattern: Local Counsel Plus a Quarterback

No single adviser can practice law or tax in multiple countries simultaneously. The professional standard that has emerged for complex cross-border families is a structure with lead counsel in each relevant jurisdiction — typically an estate attorney or tax adviser licensed to practice there — and a coordinating adviser (sometimes called a "quarterback") whose role is to ensure the various country-specific advisers are working toward a consistent overall plan rather than optimizing each jurisdiction in isolation.

Without coordination, locally sensible decisions can create serious conflicts elsewhere. A trust structure that works efficiently for U.S. estate-tax purposes may be classified as a foreign grantor trust by another country and taxed immediately upon funding. An investment account structure preferred by one country's banking system may trigger punitive reporting obligations in another. The coordinating adviser — who might be a family office CIO, a global tax partner at a large firm, or an independent consultant — holds the map of the whole terrain.

Families building this kind of team should review Building an Advisory Team and Choosing Estate Attorneys and CPAs for guidance on evaluating and organizing advisers. A family office structure, where it exists, often serves naturally as the coordinating hub.

Questions to Bring to Advisers

• In which countries is each family member a tax resident, and is anyone subject to worldwide taxation from more than one country simultaneously?
• What marital property regime governs the couple's assets, and has it shifted as the family moved between countries?
• Are any assets — real estate, business interests, retirement accounts — held in a country that imposes forced-heirship rules?
• Does a bilateral tax treaty exist between the relevant countries, and does it cover estate and gift taxes as well as income?
• Is each country's adviser aware of what the others are planning, and is there a single person responsible for overall coordination?
• What would happen to the family's plan if one member changed residency — moved back, relocated for work, or retired abroad?

Cross-border family planning is one of the few areas of wealth management where a well-intentioned decision in one jurisdiction can create an unintended crisis in another. A qualified attorney and CPA familiar with each relevant country must evaluate any particular family's situation before action is taken.