What is Dual Resident?

How it works

Each country defines residence on its own terms. The result: the same person can satisfy the residence test in two countries at once. Common ways to land in dual residence:

• 183-day test in country A + permanent-home test in country B. Spend 200 days in Spain; keep the family home and spouse in France. Both Spain (presence) and France (article 4B foyer) claim you.
• Mid-year move. Resident in Germany January-June, then move to Switzerland and become Swiss-resident from July. Without explicit split-year provisions, you can be a full-year resident of both under their domestic counts.
• Citizenship-based + residence-based overlap. A US citizen living in the UK is US-resident (citizenship-based) and UK-resident (SRT). Dual residence by construction.
• Different statutory triggers. Italy: 183 days OR domicilio civile OR residenza anagrafica. Spain: 183 days OR centre of economic interests. Easy to trip both with the same facts.

Without a tax treaty, dual residence means both countries tax worldwide income. Foreign tax credits soften the impact but rarely eliminate it. With a treaty, the OECD-style tie-breaker assigns single residence:

1. Permanent home — country where one is available.
2. Centre of vital interests — if homes in both.
3. Habitual abode — if vital interests evenly split.
4. Nationality — if habitual abode is unclear.
5. Mutual agreement procedure (MAP) between competent authorities.

The treaty tie-breaker assigns residence for treaty purposes only. The "losing" country still has the right to tax sourced income (real estate, business presence, etc.), but loses worldwide-income claim over the individual.

Citizenship override

Most US tax treaties contain a "saving clause" that preserves the US's right to tax its citizens regardless of treaty residency. So a dual US/UK resident who wins UK residency under the tie-breaker still owes US worldwide tax under §1 of the IRC — the treaty stops US-source double tax via the foreign tax credit but doesn't shield him from the US filing burden.

Examples

• French-German cross-border consultant. Lives 200 days in Strasbourg, 165 days in Karlsruhe with a German rental. Both countries are domestic-law residents. France-Germany treaty applies the tie-breaker: France probably wins on permanent home + family in Strasbourg. Germany loses worldwide-tax claim, retains tax on the German-source consulting income.
• US citizen executive in London. Both countries claim worldwide tax. Treaty tie-breaker resolves to UK on vital interests. UK now has primary worldwide-tax claim, US has secondary (saving clause). Foreign tax credit each direction reduces double tax to near-zero in practice; double-filing burden remains.

Common mistakes

• Treating dual residence as automatic dispute. It isn't — many founders are dual-resident for entire tax years and don't realise until they get a letter from the second country.
• Assuming the treaty does the work automatically. Treaty residency must usually be claimed, often via Form 8833 in the US or equivalent in other countries. Without the claim, both countries may continue to tax worldwide.
• Forgetting source-tax rights survive the tie-breaker. Winning the tie-breaker doesn't kill the other country's right to tax your local rental income, employment income from a local employer, etc. The treaty allocates worldwide vs. source.
• Ignoring the no-treaty case. Brazil, Argentina, and several other countries have limited US treaty coverage. Dual residence with no treaty means uncoordinated double tax — relief depends on each country's unilateral foreign-tax-credit rules, which are often partial.