Yes, you can hold dual citizenship in the UK and US at the same time. Both governments allow their citizens to acquire the other country’s nationality without giving up the original, and neither will strip your existing citizenship just because you naturalized somewhere else. The complications are practical rather than legal: two tax systems, passport rules at each border, and a consulate that can do less for you when you’re standing on the soil of your “other” country.
How Each Country Permits It
On the American side, the rule traces back to the Supreme Court’s 1967 decision in Afroyim v. Rusk, which held that Congress cannot strip a person of citizenship without their voluntary consent.1Justia. Afroyim v. Rusk, 387 U.S. 253 (1967) Before that ruling, acts like voting in a foreign election or naturalizing abroad could cost an American their citizenship. Today the State Department presumes that a US citizen who acquires foreign nationality intends to keep their American citizenship. Losing it requires walking into a US embassy and formally renouncing.
The UK is just as direct. The government states that dual citizenship is allowed and that you do not need to give up British citizenship when you become a citizen of another country.2GOV.UK. Dual Citizenship There is no separate application for dual status. You acquire the second nationality and your British citizenship continues uninterrupted.
What About the US Oath of Renunciation?
The Oath of Allegiance taken at a US naturalization ceremony includes language about “absolutely and entirely” renouncing allegiance to foreign sovereigns. This alarms many British applicants. In practice it does not revoke British citizenship, because UK law does not recognize a foreign oath as a ground for losing British nationality.2GOV.UK. Dual Citizenship You leave the ceremony holding both.
The Tax Reality Is the Real Cost
The single most important thing to understand before taking on a second citizenship is the tax asymmetry. The United States taxes based on citizenship. The United Kingdom taxes based on residence. That means an American who moves to London still owes annual returns to the IRS. A Briton who moves to New York owes taxes only to the IRS, because HMRC stops taxing them once they’re no longer a UK resident.
Worldwide Income Reporting for US Citizens
Every US citizen must report worldwide income to the IRS regardless of where they live.3Internal Revenue Service. U.S. Citizens and Residents Abroad – Filing Requirementsa> The United States is one of only two countries in the world that does this. Two mechanisms soften the double-taxation problem. The Foreign Earned Income Exclusion for 2026 lets you exclude up to $132,900 of foreign earnings from US tax.4Internal Revenue Service. Figuring the Foreign Earned Income Exclusion Beyond that, the US-UK tax treaty allows a credit for income taxes paid to the UK, which generally prevents the same income being taxed twice.
FBAR and FATCA
This is where many dual citizens get caught out. If your foreign financial accounts (bank accounts, investment accounts, pensions) have a combined balance over $10,000 at any point in the year, you must file a Report of Foreign Bank and Financial Accounts, known as the FBAR, by April 15 with an automatic extension to October 15.5Internal Revenue Service. Report of Foreign Bank and Financial Accounts (FBAR) A modest UK current account plus a workplace pension crosses that threshold easily.
The penalties are steep. A non-willful violation carries a civil penalty of up to $16,536 per account per year under the current inflation-adjusted schedule.6eCFR. 31 CFR 1010.821 – Penalty Adjustment and Table Willful violations are dramatically worse. Dual citizens who discover the requirement late typically have to use one of the IRS’s voluntary disclosure programs to get current.
Separately, the Foreign Account Tax Compliance Act (FATCA) requires foreign financial institutions to report accounts held by US persons to the IRS.7Internal Revenue Service. Foreign Account Tax Compliance Act (FATCA) If you live abroad and your foreign financial assets exceed $200,000 on the last day of the tax year, or $300,000 at any point during the year, you must also file Form 8938 with your tax return. Those thresholds double for joint filers.8Internal Revenue Service. Do I Need to File Form 8938, Statement of Specified Foreign Financial Assets Yes, this overlaps with the FBAR. You may need to file both.
UK Filings for Non-Residents
Because the UK taxes on residence, once you’re no longer resident you generally fall out of the UK tax system on non-UK income. UK-source income (like rental income from a British property or a UK pension) can still be taxable in the UK regardless of where you live. This is a much smaller ongoing burden than the American side.
Passports and Border Rules
Use your US passport to enter and leave the United States, and your British passport to enter the United Kingdom. This is not optional. US law requires American citizens to use a US passport to enter the country, and UK border control expects to see a British passport or proof of right of abode. In practice you carry both passports when flying between the two, and airlines may ask to see the passport valid for your destination before boarding.
Consular Protection Is Limited in Your Other Country
Most dual citizens don’t think about this until they need help. When you’re in the UK, the US embassy’s ability to assist you is sharply restricted. Under generally recognized international law, the country where you are present has the predominant claim on you as its national. The State Department will still try to help, but acknowledges its representations may or may not be accepted by the UK government.9U.S. Department of State. 7 FAM 080 Dual Nationality The same works in reverse: a British consulate in New York has limited leverage if an American-British dual citizen runs into trouble on US soil. For everyday matters this never comes up. If you were detained or faced a serious legal dispute, you would effectively be treated as a local rather than a foreigner.
Passing Citizenship to Children Born Abroad
Each country has its own rules on whether your child born outside your home country automatically becomes a citizen.
US Transmission
For a child born abroad to one US citizen parent and one non-citizen parent, the American parent must have been physically present in the United States for at least five years before the child’s birth, with at least two of those years after age 14.10U.S. Department of State. 8 FAM 301.7 Immigration and Nationality Act of 1952 If both parents are US citizens, only one needs to have resided in the US at some point before the birth. The child acquires citizenship at birth but it still needs to be documented, typically by filing a Consular Report of Birth Abroad at a US embassy.
UK Transmission
UK law hinges on how the parent became British. If you were born in the UK or naturalized there, you are “British otherwise than by descent,” and your children born abroad automatically acquire British citizenship. If you yourself were born abroad and are “British by descent,” your children born outside the UK do not automatically get it. You can register them if you lived in the UK for three years at any point before the child’s birth, but the child will also be British by descent and cannot pass citizenship on to their own children born abroad. Breaking that one-generation limit requires moving the family to the UK and living there for three years, after which the child can be registered as British otherwise than by descent.
Voting, Government Jobs, and Security Clearances
Dual citizens keep the right to vote in national elections in both countries. Americans abroad vote in federal elections by registering in the last state where they lived. British citizens overseas can register as overseas voters, and a 2024 change removed the previous 15-year cap on that right. Local elections in either country generally require local residence.
Dual citizenship does not automatically disqualify you from a security clearance on either side, but it adds scrutiny. In the US, clearance decisions follow Security Executive Agent Directive 4 (SEAD-4). Adjudicators evaluate foreign preference and foreign influence, so holding a second passport is permitted, but using it, voting in foreign elections, or accepting foreign government benefits like a UK State Pension can raise flags that need explanation.11Office of the Director of National Intelligence. Security Executive Agent Directive 4 Adjudicative Guidelines In the UK, higher-level vetting such as Developed Vetting carries a standard expectation of ten years of UK residency, though cases are assessed individually.12GOV.UK. Vetting and Nationality and Travel Both systems reward candor and penalize concealment.
The Bottom Line Before You Apply
Legally, holding both citizenships is straightforward and secure. The decision that actually matters is whether you are prepared for lifelong US tax filings if you take on American citizenship, or for the paperwork of maintaining British status from abroad. Anyone considering the move should model the tax and reporting side with a cross-border accountant before filing the naturalization forms, not after.