Citizenship-based taxation is a tax system where a country taxes its citizens on their worldwide income regardless of where they live or where the income is earned. If you're a citizen working and living abroad, you're liable for taxation in your home country and must file tax returns and pay taxes even if you reside permanently elsewhere.
Citizenship-based taxation is extraordinarily rare. Only two countries practice it: the United States and Eritrea. Every other country uses residency-based taxation—you're taxed on worldwide income only if you're a tax resident of that country. This makes citizenship-based taxation a defining (and unpopular) feature of the U.S. tax system and a major driver of demand for second passports among Americans abroad.
The U.S. has practiced citizenship-based taxation since the income tax was introduced in 1913. Eritrea, having gained independence in 1993, adopted a similar system partly modeled on the U.S. approach. No other country has followed suit. Why? Because it's administratively complex, enforces tax sovereignty that other countries find incompatible with modern international norms, and creates friction with citizens living abroad, many of whom eventually renounce citizenship specifically to escape the tax burden.
U.S. citizens and residents must file tax returns with the IRS on their worldwide income. This applies regardless of where you live—whether in Canada, Australia, the Middle East, or anywhere else. A U.S. citizen living in Singapore earning a salary from a Singaporean employer must still file a U.S. tax return and potentially pay U.S. income tax.
But the U.S. tax code includes a Foreign Earned Income Exclusion (FEIE), which allows U.S. citizens living abroad to exclude approximately $126,500 (as of 2025) of foreign earned income from U.S. taxation, provided they meet either the Physical Presence Test (spending at least 330 days outside the U.S. in a 12-month period) or the Bona Fide Resident Test (being a tax resident of another country for an entire tax year). This exclusion significantly reduces the tax burden for many Americans abroad but doesn't eliminate it. Income above the FEIE threshold, investment income, and capital gains remain subject to U.S. taxation.
Additionally, the Foreign Account Tax Compliance Act (FATCA) requires U.S. citizens to report all foreign financial accounts exceeding $10,000 in aggregate value. Failure to file these FBAR forms results in substantial penalties—up to 50% of the account balance for willful violations. This creates an enormous compliance burden, particularly for Americans living abroad who may hold accounts with non-U.S. financial institutions.
The U.S. has negotiated over 60 bilateral tax treaties with other countries to prevent double taxation. These treaties typically provide tax credits: if you pay tax in country A and also owe tax to the U.S. on the same income, you can claim a credit for taxes paid to country A, reducing your U.S. liability. The mechanics are complex, though, and in some cases—particularly involving investment income—double taxation can still occur despite treaty protections.
If you live in Singapore and earn significant dividend income, Singapore may tax the dividends at a low rate, but the U.S. taxes them at a higher rate. The tax treaty provides mechanisms to claim credits, but calculating this correctly requires sophisticated tax planning. Many Americans abroad hire U.S. tax specialists (CPAs or enrolled agents) costing $1,500–$5,000+ annually just to correctly file their taxes and minimize double taxation.
The Foreign Account Tax Compliance Act, enacted in 2010, extended U.S. citizenship-based taxation worldwide by requiring foreign financial institutions to report information about U.S. account holders to the IRS. Banks and investment firms worldwide must identify U.S. persons, report their accounts to the IRS, and withhold 30% of certain payments if they fail to comply. This created significant friction with foreign banks.
Many foreign banks have simply closed the accounts of U.S. citizens rather than comply with FATCA's reporting requirements, particularly in smaller financial centers where the compliance burden outweighs the business volume. This has made it substantially harder for Americans abroad to access banking services, investment accounts, and mortgages. Some countries have resisted FATCA implementation or limited it, but FATCA's reach is extensive and continues to expand as more countries sign intergovernmental agreements.
The U.S. imposes an "exit tax" on U.S. citizens who renounce citizenship or long-term residents who abandon residency. The exit tax applies to "covered expatriates"—those with an average income tax liability exceeding approximately $190,000 for the five years prior to departure or with net worth exceeding $2 million. These individuals must pay a mark-to-market tax on all their worldwide assets as if they had sold them on the date of departure, even though they haven't actually sold anything. This "deemed gain" is taxable.
For a wealthy individual renouncing citizenship, the exit tax can be substantial. If you have a portfolio of appreciated assets (stocks, real estate, business interests) worth millions, the exit tax could force you to pay hundreds of thousands or millions in taxes, even though you're not actually selling the assets. This is a significant financial consideration for wealthy Americans considering renunciation.
Additionally, the U.S. maintains the Reed Amendment, which theoretically bars covered expatriates from re-entering the U.S., though this provision is rarely enforced. The practical impact is that renouncing citizenship is a serious, relatively irreversible decision with significant tax consequences.
Citizenship-based taxation is the primary reason Americans represent a disproportionately large share of CBI applicants. A U.S. citizen living permanently in Singapore or Malta faces an indefinite tax burden to the U.S. government. The combination of citizenship-based taxation, FATCA compliance, and Foreign Earned Income Exclusion complexity creates a strong incentive to acquire second citizenship in a country with low or no personal income tax, allowing the person to structure their affairs to minimize double taxation.
For Americans with substantial international income or assets, acquiring citizenship in a low-tax jurisdiction like Malta, Portugal (which has a non-habitual resident program), or a Caribbean nation provides significant tax planning flexibility. This doesn't eliminate U.S. taxation but can substantially reduce it when combined with residency-based tax planning.
Furthermore, some Americans consider renouncing U.S. citizenship. CBI programs provide a practical path: acquire citizenship in another country first, then renounce U.S. citizenship from a position of strength (with alternative citizenship already secured). This is a primary driver of U.S. citizen interest in Caribbean CBI programs.
The rest of the world uses residency-based taxation, where you're taxed on worldwide income only if you're a tax resident of that country. Tax residency is typically determined by tests such as the 183-day rule (spending more than 183 days in a calendar year in a country) or by permanent residence status. This system allows people to migrate to low-tax jurisdictions and immediately reduce their tax burden, subject only to that new jurisdiction's tax rules. For non-Americans, second citizenship or residency acquisition primarily enables visa-free travel; tax benefits are secondary. For Americans, tax planning is often the primary motivation.