Dual citizenship provides significant flexibility in travel, business formation, and life planning, but it can create equally complex tax implications. Some countries structure taxation based on residency, while others base it on citizenship. Consequently, while the perception of "two passports = double taxes" often does not fully reflect reality, adapting to two separate tax systems becomes inevitable for many.
In this article, we will examine step by step how dual citizenship changes tax obligations, particularly the risks arising from the US citizenship-based taxation system and the mechanisms that prevent double taxation. We will also share a practical checklist for those planning global mobility (relocating abroad, business formation, payroll/EOR, posted workers).
Why does dual citizenship change tax obligations?
Tax obligations are not determined solely by "which passport you hold." In most countries, the key factors are:
- Tax residency: How many days of the year you spend where, where your "center of life" is, family/business ties, and similar criteria.
- Source of income: Where the income originates (where salary is paid, where work is actually performed, where the property is located, etc.).
- Citizenship: While only a few countries consider this determinative, it is a critical factor in exceptional cases like the US.
Dual citizenship, especially when one country requires reporting based on citizenship while another taxes based on residency, can create a requirement to file in two separate countries for the same income. In most cases, this does not mean "paying tax twice"; however, it does create two separate compliance burdens.
Why does the US create a "special case" for dual citizens?
The United States is one of the rare countries that applies citizenship-based taxation. In this system, if you are a US citizen (or in some cases a green card holder), you may have a US tax obligation on your worldwide income regardless of where you live. Holding a second passport does not automatically eliminate this obligation.
Additionally, there is an important distinction on the US side: tax liability is not the same as filing requirements. Even if your tax liability is "zero" after deductions and credits are applied, you may still be required to file if you exceed certain thresholds.
US filing thresholds (2025)
For US citizens, federal income tax filing in 2025 generally comes into play at these thresholds:
- Single / separately: 15,750 USD
- Married filing jointly: 31,500 USD
- Head of household: 23,625 USD
In short: A dual citizen who is a US citizen must keep the annual filing process on the agenda, regardless of where they reside.
"Will I pay taxes to both countries?": 3 main mechanisms to prevent double taxation
While dual citizens theoretically appear to pay taxes to both countries, in practice there are tools to prevent double taxation. The three main mechanisms from a US perspective are:
1) Foreign Earned Income Exclusion (FEIE)
FEIE (Foreign Earned Income Exclusion) allows individuals who meet the qualifying conditions to exclude a portion of wages and self-employment income earned abroad from US taxation. According to research data, the exclusion amount for 2025 is approximately 130,000 USD.
To benefit from FEIE, you generally need to pass one of two tests:
- Physical Presence Test: Being abroad for at least 330 days during a 12-month period
- Bona Fide Residence Test: Establishing a permanent residence abroad for an entire tax year
For example, a US-born dual citizen currently living in London and earning 105,000 USD from UK sources can exclude all of this income from US taxation under FEIE if they meet the conditions, reducing their US tax liability to zero.
Important note: FEIE generally reduces tax liability; however, it does not eliminate filing and reporting requirements.
2) Foreign Tax Credit (FTC)
FTC (Foreign Tax Credit) allows income taxes paid to another country to be deducted from your US tax liability. This "dollar-for-dollar" mechanism is particularly effective for those living in countries with higher tax rates than the US.
The logic works like this:
- US tax liability: 500 USD
- Tax paid to another country: 300 USD
- Credit available through FTC: 300 USD
- Final payment to the US: 200 USD
In countries like the United Kingdom, where income tax rates (20%, 40%, 45% brackets for 2025-26) generally exceed US federal tax in most scenarios, FTC often produces more favorable results than FEIE. However, this assessment is determined by income type, family status, deductions, and investment income variables.
3) Tax Treaties
Tax treaties (double tax treaties) clarify how specific income types are taxed by each country. Treaties such as the US-UK tax treaty may contain special provisions on retirement income, social security, and investment gains.
The critical point is this: simply "relying on" a tax treaty may not be sufficient. In practice, you may need to report treaty positions properly on the US side using the correct forms (research data mentions Form 8833 as an example). Otherwise, compliance risks may arise later.
How does the country of the second citizenship generally tax?
Unlike the US, many countries tax based on residency rather than citizenship. For example, someone living in the United Kingdom is subject to UK tax on income earned in the UK or from UK sources. For dual citizens, this typically means:
- Filing and payment in the country of residence,
- If a US citizen, separate annual filing to the US,
- Using FEIE/FTC/treaty provisions to optimize and prevent double taxation.
Therefore, the question should often not be "Will I pay taxes in both countries?" but rather "To what extent must I file in both countries, and which mechanism will I use to prevent double taxation?"
Foreign financial accounts: FBAR and FATCA obligations
One of the most frequently overlooked areas for dual citizens involves financial account reporting, which operates separately from income tax filing. According to research data, two key areas stand out:
- FBAR (FinCEN Form 114): If the aggregate total of foreign financial accounts exceeds 10,000 USD at any point, reporting may be required.
- FATCA (Form 8938): If foreign financial assets exceed certain thresholds, an additional form may be required.
These forms create a "easy to overlook but serious consequences" risk area due to technical details and thresholds. When bank accounts, investment accounts, and certain asset types are not properly classified, compliance risk increases.
Tax-advantaged local products may not be advantageous in every country
Dual citizens, especially those with US ties, should verify whether products known as "tax-exempt in my country" are treated the same way in the US. Research data highlights ISA accounts in the UK as an example: while these provide tax advantages in the UK, they may be taxable in the US or trigger different reporting expectations.
For this reason, when planning internationally, you should not proceed solely with your local bank's or local advisor's perspective, but rather with an approach that simultaneously considers both countries' tax regulations.
Practical process: How should dual citizens manage tax compliance?
Tax compliance for dual citizens becomes manageable when you establish a good "annual routine." The following steps are particularly useful for those with US ties:
1) Clarify your residency picture
- How many days did you spend in each country during the year?
- Where is "the place where work is performed" according to your employment contract?
- Where are your family/home/permanent arrangements located?
2) Classify your income types separately
- Salary / bonus
- Self-employment / consulting
- Rental income
- Dividends / interest / capital gains
- Retirement and similar recurring payments
3) FEIE or FTC? Calculate scenario-based
FEIE provides quick relief in some profiles; FTC may be more effective in high-tax jurisdictions. Choosing incorrectly, while not creating a legal problem, can create unnecessary tax costs.
4) Treat additional filings (FBAR/FATCA) as "separate work"
View these items not as an extension of your income tax return, but as a separate compliance area with its own checklist.
5) Establish calendar and document management
For individuals filing in dual countries, regular document archives (payroll slips, tax assessments, bank statements) and calendar management significantly reduce errors.
The tax dimension becomes even more critical for those forming companies and sending teams abroad
While dual citizenship alone creates complexity, when international business formation or employee mobility enters the picture, the scope expands:
- Where an employee actually performs their work can affect income tax and social security burdens.
- Payroll processes (payroll/EOR) in different countries create different filing and withholding rules.
- In models like "posted workers," tax optimization must comply strictly with regulations.
- The risk of your company having a "permanent establishment" in another country can trigger corporate taxation.
Corpenza supports employers and individuals in managing this multi-layered structure more predictably through end-to-end solutions such as business formation, residency & investment programs, international accounting, payroll/EOR, and posted worker models across Europe and globally. Especially in structures earning income in multiple countries, relocating abroad, or expanding teams to different countries, addressing tax compliance and operational design together clearly reduces costs and risks.
Conclusion: Dual citizenship changes tax "management," not tax burden
Dual citizenship does not always mean double taxation; however, it often means a double compliance process. For dual citizens who are US citizens, annual filing, FEIE/FTC/treaty evaluation, and reports like FBAR/FATCA are not optional—they are essential parts of planning.
The healthiest approach is to conduct a scenario-based evaluation according to your residency, income types, and asset structure, and support decisions with documentation. For individuals with international business and life plans, professional support helps manage not only tax costs but also compliance risks.
Disclaimer
This content is for general informational purposes only; it does not constitute legal, financial, or tax advice. Tax regulations vary by country and individual circumstances and may change over time. Before taking any action, please check current official sources and consult with a qualified professional in the relevant field.
