Tax
Tax Residency
Also known as: Tax Resident, Fiscal Residency, Residency for Tax Purposes
Tax residency is a fiscal concept distinct from immigration residence (a residence permit) and citizenship. Each country's tax authority defines its own test for when an individual becomes "resident for tax purposes" — and once you cross that threshold, the country generally claims taxing rights over your worldwide income (under the worldwide-taxation model adopted by most developed nations).
Common residency tests:
• 183-day rule (most common). Spending 183 or more days in the country during the tax year (sometimes counted across rolling 12-month periods) typically triggers tax residency. Used by Spain, France, Germany, UK (combined with the Statutory Residence Test), Portugal, Italy, Japan, Singapore, etc. The day-counting rules vary: the day of arrival, day of departure, and partial days are treated differently across jurisdictions.
• Domicile-based (UK historically, abolished from April 2025; some Caribbean states). Tax residency based on a more stable concept of "permanent home," which can outlast physical presence.
• Centre-of-vital-interests / centre-of-economic-interests. Many countries supplement the day count with a deemed-residence rule when the individual's family, primary home, or main income source is in the country.
• Substantial Presence Test (US-specific). The US uses a weighted formula (current year days + 1/3 of prior year + 1/6 of year-before-that ≥ 183).
Dual tax residency is the practical issue for most expats. Spending 200 days in Spain and 165 in Portugal during the same calendar year can make you tax resident in BOTH under each country's domestic rules. Tax treaties resolve these conflicts via tie-breaker rules: typically (1) where you have a permanent home, (2) where your centre of vital interests is, (3) where you habitually reside, (4) of which you are a national, and (5) competent-authority resolution. A determination one way or the other has substantial real-world consequences for which country taxes pension income, rental income, dividends, and capital gains.
For US citizens and green-card holders, US tax residency is permanent regardless of where you live: the US taxes worldwide income for life until citizenship is renounced or the green card is formally surrendered. Other tax residencies layer on top of this US baseline, with FEIE / FTC / treaties as the mitigation tools.
Sources
- OECD Model Tax Convention — Article 4 (Resident)
- IRS — Determining an Individual's Tax Residency Status
Last factual review: 2026-05-08.
Related terms
Substantial Presence Test (SPT)
The Substantial Presence Test is the IRS's primary test for determining whether a non-US citizen is a US tax resident. It applies a weighted formula: count all days physically present in the US in the current year + 1/3 of days in the prior year + 1/6 of days two years prior. If the total reaches 183, you are a US tax resident — subject to certain exemptions and the closer-connection exception.
Tax Treaty
A tax treaty is a bilateral agreement between two countries that allocates taxing rights over cross-border income, prevents double taxation, and provides mechanisms to resolve disputes. Treaties typically follow the OECD or UN Model Convention. The US has tax treaties with about 70 countries; the UK with about 130. Treaty benefits often require formal claim on a tax return (e.g., IRS Form 8833 for treaty-based positions on a US return).
FEIE (Foreign Earned Income Exclusion)
FEIE lets US citizens and resident aliens exclude up to $132,900 (2026) of foreign-earned income from US federal income tax — but not from Social Security/self-employment tax. To qualify, the taxpayer must meet either the Bona Fide Residence Test (full-year tax residence in a foreign country) or the Physical Presence Test (330 full days abroad in any 12-month period). Claimed on IRS Form 2555 attached to Form 1040.
Foreign Tax Credit (FTC)
The Foreign Tax Credit lets US citizens and resident aliens reduce their US tax liability dollar-for-dollar by income taxes already paid to foreign governments on the same income. Claimed on IRS Form 1116, it prevents double taxation on income above the FEIE ceiling and on passive income that FEIE doesn't cover. The credit is per-category, capped at the US tax otherwise due on the foreign-source income, with 10-year carryforward and 1-year carryback for unused credits.
Double Taxation
Double taxation occurs when the same income or capital is taxed twice — typically once by the source country (where the income arises) and once by the residence country (where the recipient is tax resident). It's prevented by tax treaties (which allocate taxing rights) and by domestic relief mechanisms like the foreign tax credit and the foreign earned income exclusion. Unrelieved double taxation is rare in modern tax systems but can still occur with non-treaty-partner countries.
Deeper guides
Switzerland Lump-Sum Taxation 2026: Residency via Annual Tax Negotiation
Switzerland's forfait fiscal / pauschalbesteuerung grants residence to non-Swiss nationals who negotiate a fixed annual tax contribution (typically CHF 150-450K depending on canton). No capital investment required; the annual tax IS the qualifying contribution. Must not have been Swiss tax resident in 10 years prior and cannot earn Swiss-source income during the regime. Actual Swiss residence required (183+ days). Full canton-by-canton analysis including the 2009 Zurich and 2014 Basel-Stadt abolitions.
US State Taxes After Moving Abroad: Which States Follow You (and How to Break Free)
California, New York, Virginia, South Carolina, and New Mexico pursue expats for state taxes after moving abroad. The FEIE does NOT protect you. Here's the 7-step checklist to cleanly break state tax residency before you leave — plus the self-employment tax trap that catches freelancers even with FEIE.
The Slowmad Tax Trap: How Splitting Time Between Countries Creates Tax Nightmares
The 183-day rule is not universal. France's permanent home test, Germany's habitual abode, Portugal's rolling 12-month period, and the US weighted formula can all trigger tax residency with fewer days than you think. Safe patterns vs risky patterns, the Estonia-Georgia structure, and why a $3K-5K/year tax advisor is cheaper than $10K-50K+ in back taxes.
Best Low-Tax Countries for Expats 2026: Spain Beckham vs. Italy Impatriati vs. UAE vs. Cyprus Non-Dom
UAE (0%), Monaco (0%), Spain Beckham (24% flat 6 yrs), Cyprus Non-Dom (0% dividends 17 yrs), Italy Impatriati (50% cut), Greece 7-year (50% cut). Every tax regime compared with 2026 rates — employment, investor, pension, crypto.
Monaco Residence Permit 2026: €500K+ Deposit, Zero Income Tax
Monaco Residence Permit (Carte de Séjour) in 2026 — €500,000+ Monaco bank deposit (remains your property), mandatory Monaco property, 3 months/year actual residence. Zero personal income tax, zero wealth tax. 10-year path to rare discretionary citizenship. Full comparison with Switzerland lump-sum taxation.
China Capital Controls Relocation Guide (2026): US$50K Quota, Jan 2026 KYC, Financing Strategy
Practical orientation on Chinese FX controls for relocating families. US$50,000 individual annual quota with declared-purpose restrictions; Jan 1, 2026 KYC/AML tightening (RMB 5,000/US$1,000 verification threshold, 10-year record retention). Household pooling, staged transfers, ODI, QDII, HK intermediate accounts, and why destination-country financing structurally matters. Not tax advice.