To become a US citizen from the UK, a British green card holder files Form N-400 after five years as a lawful permanent resident (or three years if married to a US citizen), passes an English and civics test at a USCIS interview, and takes the Oath of Allegiance at a naturalization ceremony. The United Kingdom permits dual citizenship, so you keep your British passport. The United States, in return, begins taxing you on your worldwide income for the rest of your life.
You Do Not Have to Give Up Your British Citizenship
This is the question most UK applicants ask first. The Oath of Allegiance contains language about renouncing foreign allegiances, but in practice the US government does not require you to surrender your foreign citizenship or passport. US immigration law does not explicitly prohibit dual citizenship, and taking the oath does not trigger any automatic loss of British nationality on the American side.
British law is equally permissive. Acquiring a foreign nationality does not cause you to lose your British status, and you can continue to renew your UK passport after naturalization.1GOV.UK. Dual Citizenship Most British-born Americans carry both. Use the US passport to enter and leave the United States, and the British passport when traveling to the UK.
Who Qualifies
The Immigration and Nationality Act sets the baseline. You must be at least 18 when you file Form N-400 and have maintained continuous residence in the United States as a lawful permanent resident for five years, or three years if you are married to and living with a US citizen.2Office of the Law Revision Counsel. 8 USC 1427 – Requirements of Naturalization You must also have lived in the state or USCIS district where you file for at least three months before submitting your application.
Holding the green card is not enough on its own. You need physical presence in the United States for at least half of the qualifying period: 30 months on the five-year track, 18 months on the three-year spousal track.3U.S. Citizenship and Immigration Services. Continuous Residence and Physical Presence Requirements for Naturalization
Trips Back to the UK
British citizens who travel home often need to watch the calendar. A single absence longer than six months but under a year creates a presumption that you broke continuous residence. You can rebut it by showing you kept your US home, job, and tax residence, but the burden is yours.2Office of the Law Revision Counsel. 8 USC 1427 – Requirements of Naturalization Any absence of a year or more automatically breaks continuous residence, and the clock generally restarts. Narrow exceptions exist for people employed by the US government, certain American companies operating abroad, or qualifying international organizations.
Good Moral Character
USCIS reviews your moral character for the full statutory period and through your oath ceremony. The review covers criminal history, tax compliance, and family obligations such as child support. Murder and aggravated felonies are permanent bars. Other criminal conduct may impose temporary bars or require evidence of rehabilitation before USCIS will approve you.4U.S. Citizenship and Immigration Services. Restoring a Rigorous, Holistic, and Comprehensive Good Moral Character Evaluation Standard for Aliens Applying for Naturalization
Selective Service
Male applicants aged 18 to 25 must be registered with the Selective Service System. If you are a man between 26 and 31 who never registered, USCIS will want evidence that the failure was not deliberate. After age 31 the issue falls outside the statutory period and generally no longer blocks the application.5Selective Service System. USCIS Policy Manual – Selective Service Registration Men who did not live in the United States between 18 and 26, or who held lawful nonimmigrant status throughout that period, were not required to register.
Filing Early
You do not have to wait until the day you hit five years. USCIS lets you file Form N-400 up to 90 days before you complete the continuous residence requirement. You will not be naturalized until you reach the mark, but filing early can save months.6U.S. Citizenship and Immigration Services. Chapter 6 – Jurisdiction, Place of Residence, and Early Filing
Filing Form N-400
Form N-400 is available through the USCIS online account portal at myaccount.uscis.gov.7U.S. Citizenship and Immigration Services. Apply for Naturalization The form asks for a detailed account of the past five years (or three, on the spousal track): every address, every employer, and every trip outside the United States with exact departure and return dates. Keep a log built from passport stamps or airline records. Inconsistencies between your form and border data cause delays and requests for evidence.
The filing fee is $710 online or $760 on paper.8U.S. Citizenship and Immigration Services. N-400, Application for Naturalization Online filing is cheaper and lets you track your case in real time. Paper filers can no longer pay by personal check, money order, or cashier’s check; you pay by credit, debit, or prepaid card using Form G-1450, or by direct bank transfer using Form G-1650. Reduced fees and full waivers exist for applicants with low household incomes or who receive means-tested benefits.9U.S. Citizenship and Immigration Services. Additional Information on Filing a Reduced Fee Request
Biometrics, Interview, and Timeline
After USCIS accepts your application, you receive a receipt notice and, separately, a notice scheduling biometrics at a local Application Support Center. USCIS collects new fingerprints, a photograph, and a digital signature for every N-400, even if you have prior prints on file.10U.S. Citizenship and Immigration Services. Chapter 2 – Biometrics Collection
National median processing time is roughly five to six months as of early 2026, but the range across field offices is wide. Some offices finish 80% of cases in under three months; others take 13 months or more. The USCIS Case Processing Times page shows the estimate for your field office.
The Interview
The interview is a one-on-one meeting with a USCIS officer, under oath. The officer walks through your N-400 line by line and asks you to confirm or correct your answers. That conversation also serves as the speaking portion of your English evaluation.
English and Civics Tests
You take a short reading test and a short writing test using basic vocabulary drawn from civics topics. The officer shows you up to three sentences and asks you to read one aloud, then dictates up to three and asks you to write one correctly. One right in each category passes.11U.S. Citizenship and Immigration Services. The Naturalization Interview and Test
The civics test is oral. The officer picks 10 questions from a published pool of 100 covering American history, government structure, and constitutional principles. You need 6 correct to pass. The full list of questions and answers is public, so anyone who studies knows what is coming.
Age-based exemptions from the English requirement exist for older long-term residents: over 50 with 20 years as a permanent resident, or over 55 with 15 years. Those applicants take the civics test in their native language through an interpreter.12eCFR. 8 CFR Part 312 – Educational Requirements for Naturalization A medical exemption is available through Form N-648 for applicants with a qualifying physical or mental impairment.
If You Fail
If you fail either test, USCIS reschedules you between 60 and 90 days later, and you retake only the portion you failed. A second failure results in denial, though you can refile a new N-400 and pay the fee again.13U.S. Citizenship and Immigration Services. Chapter 2 – English and Civics Testing
The Oath of Allegiance
Approval is not citizenship. You become a US citizen only when you take the Oath of Allegiance at a naturalization ceremony, no matter how long ago your case was approved.14U.S. Citizenship and Immigration Services. Naturalization Ceremonies The ceremony may be administrative, run by USCIS, or judicial, held in a federal courtroom.
You surrender your green card at check-in. After the oath you receive a Certificate of Naturalization, which is your primary proof of citizenship. Check every detail before you leave the room; corrections are far harder later. The certificate lets you apply for a US passport and register to vote.
Tax Consequences for British Nationals
The single change most likely to catch a UK national off guard is tax. The United States taxes citizens on worldwide income, so bank accounts, investments, and pensions you still hold in Britain become reportable to the IRS whether or not they generate US tax.
FBAR
If the combined value of all your foreign financial accounts exceeds $10,000 at any point during the year, you must file FinCEN Form 114 (the FBAR) with the Financial Crimes Enforcement Network. This applies even when the accounts earn nothing taxable. The deadline is April 15 with an automatic extension to October 15, and penalties for non-filing are severe.15Internal Revenue Service. Report of Foreign Bank and Financial Accounts (FBAR)
FATCA (Form 8938)
Separately from the FBAR, you may need to file Form 8938 with your tax return. For taxpayers living in the United States, the trigger is $50,000 in foreign financial assets on the last day of the year or $75,000 at any point during the year, doubled for married couples filing jointly.16Internal Revenue Service. Do I Need to File Form 8938, Statement of Specified Foreign Financial Assets FBAR and FATCA overlap, and you often report the same accounts on both.
ISAs and UK Pensions
This is where British nationals get hit hardest. A UK Individual Savings Account is tax-free under British law, but the IRS does not recognize the shelter. Interest, dividends, and capital gains inside your ISA are taxable on your US return. If the ISA holds UK mutual funds, those funds are likely Passive Foreign Investment Companies under US tax law, which triggers punitive tax rates and requires filing Form 8621 for each fund, every year you hold it. Many cross-border tax advisers suggest liquidating UK investment accounts after naturalization and reinvesting through US-based alternatives. It is worth paying for cross-border tax advice before your oath ceremony rather than after.
Social Security and the UK State Pension
The United States and the United Kingdom have a totalization agreement that lets you combine work credits from both countries when you might not qualify on either system alone. To use UK credits toward US Social Security you need at least six US credits, roughly a year and a half of covered US employment. To use US credits toward the UK basic state pension you need at least one year of UK coverage.17Social Security Administration. Totalization Agreement with United Kingdom
Each country pays its own benefit based on credits earned under its own system. If you already qualify for US Social Security on your American work record alone, the agreement will not add your UK credits on top. US credits count only toward the UK basic state pension, not the additional second-tier pension. Naturalizing as an American does not affect your UK state pension entitlement; that turns on the National Insurance contributions you made while working in Britain.
Children Under 18
If you have children under 18 who are lawful permanent residents living in your legal and physical custody in the United States, they become US citizens automatically the moment you take the oath. Under the Child Citizenship Act, no separate application is needed, but you should file Form N-600 to obtain a Certificate of Citizenship as proof.18eCFR. Part 320 – Child Born Outside the United States and Residing Permanently in the United States; Requirements for Automatic Acquisition of Citizenship Adopted children qualify under the same framework if they meet the adoption requirements of the Immigration and Nationality Act.