Citizenship and passports: how nationality is gained, kept and given up

What this flag means

The citizenship flag is the nationality, or nationalities, a person holds and the passports that prove it. Nationality is granted under each country's own law, usually at birth through birthplace or parents, later through naturalization after lawful residence, sometimes through marriage, and in a few countries through payment or investment. It can carry rights, such as entering and living in that country, and duties, such as filing obligations or military service, that apply wherever the person lives. Giving it up is a separate legal act with its own consequences.

Know the main routes to citizenship

Countries grant nationality through a small number of route families. The names and conditions differ, so treat this as a map of the questions, not a list of rules that apply everywhere.

Official sources draw the same line. US guidance, for example, separates naturalization, which it describes as citizenship granted to a lawful permanent resident who meets the conditions set by Congress, from acquisition through citizen parents at birth or after birth before age 18.

• Descent or ancestry: citizenship through a parent, and in some countries through a grandparent or earlier generation. Some countries confer it automatically at birth. Others require registration, and the registration date can matter. Proof is usually a chain of civil records.
• Naturalization: citizenship granted after a period of lawful residence, often with language, knowledge, character and presence conditions. The residence period, the counting method and the allowed absences are set by each country's law.
• Marriage or civil partnership: in most systems this is a modified naturalization route with its own conditions, not an automatic grant. Check whether a period of marriage, cohabitation or residence is required.
• Investment: a few states grant nationality in exchange for a payment or investment. These programs change, close or face legal challenges, so check the current law and official program page, not a sales brochure.

Keep citizenship, immigration permission and tax residence apart

Three different legal questions are often blurred together. Citizenship says which state you belong to. Immigration permission says where you may live and work. Tax residence says which country taxes you as a resident. Each is decided by different rules, and often by different authorities.

They can still touch each other. In the United States, holding lawful permanent resident status (a green card) is itself one of the two tests that make a non-citizen a US tax resident, and the US taxes its citizens on worldwide income wherever they live. In the United Arab Emirates, a valid residence permit is one condition in one of the tax residence tests, not a test on its own. See Living base for residence permission and Tax residency for how residence for tax is decided.

Check whether each country accepts dual citizenship

Dual citizenship has two sides. The country you already belong to decides whether you keep its nationality when you take another. The country you join decides whether you must give up the old one. Both answers matter, and they can differ.

The United Kingdom, for example, allows dual citizenship. Its official guidance also warns that many countries do not, and tells readers to check that country's dual nationality law with its consulate or embassy. Some countries treat voluntarily taking another nationality as a ground for losing theirs. Check the current law of every country involved before you apply, not after.

Understand what giving up citizenship does

Renunciation is a formal legal act, and reversing it is often difficult or impossible. Many countries require you to hold, or be about to receive, another nationality first so that you do not become stateless. UK guidance, for example, allows renunciation only if you already have another citizenship or will get one.

For the United States, federal law lists formal renunciation before a US diplomatic or consular officer in a foreign country as an act of expatriation, if done voluntarily and with the intention of giving up nationality. Renouncing does not erase past US tax obligations.

The IRS expatriation tax rules (Internal Revenue Code sections 877 and 877A) apply to US citizens who renounce and to certain long-term residents who end their status. A person can be a covered expatriate if their average annual net income tax for the five prior years is above an inflation-adjusted amount, if their net worth is 2 million US dollars or more on the expatriation date, or if they cannot certify on Form 8854 that they met their US federal tax obligations for the five prior years. A covered expatriate's property is generally treated as sold the day before expatriation. Until the IRS is notified on Form 8854, a person may still be treated as a US citizen for tax purposes. The thresholds change each year: check the current Form 8854 instructions.

Look at investment routes with extra care

Residence by investment and citizenship by investment are different things. The first gives permission to live in a country, and a path to nationality, if one exists, still runs through that country's normal naturalization law. The second grants nationality directly.

Investment routes sit under legal and political pressure. On 29 April 2025 the Court of Justice of the European Union held that Malta, by setting up and running a citizenship by investment scheme that granted nationality in exchange for predetermined payments or investments, failed to fulfil its obligations under Article 20 TFEU and Article 4(3) TEU. Programs elsewhere can be changed, paused or closed.

An investment passport does not change where you are tax resident. Financial institutions report account information under the automatic exchange rules based on tax residence, which is a separate question from which passports you hold. See Banking.

Read passport rankings for what they measure

Passport rankings mostly count how many destinations a passport can enter without a visa arranged in advance. Each destination sets its own entry rules and can change them at any time, so a ranking is a snapshot of other countries' policies.

A ranking does not tell you the things that usually matter more for a decision:

• Whether you may live, work or study in a destination, not just visit.
• What duties come with the nationality, such as filing obligations wherever you live (the United States taxes its citizens on worldwide income) or military service.
• Whether your current country lets you keep its nationality if you take this one.
• Whether the nationality can pass to your children, and on what conditions.
• How the country treats its nationals abroad, including consular help.
• Whether the route used to get it, such as an investment program, is under legal challenge.

Gather documents before you speak to a lawyer

Most citizenship questions turn on documents. A lawyer can answer faster and more accurately if the records are already together. Official copies and certified translations are often required, and some countries require an apostille or consular legalization.

• Birth, marriage, divorce and death certificates for you and the relevant parents or grandparents.
• Old and current passports and naturalization certificates for each person in the chain.
• Evidence of any earlier loss, renunciation or registration of nationality.
• A residence history with dates, permit types and absences, if naturalization is the route.
• Name changes and spelling differences between records, with the documents that explain them.

Common misconceptions

Questions to take to a professional

1. Under the nationality law of each country involved, which route, if any, fits my family history or residence history, and which documents prove it?
2. Does each country I hold, or would join, accept dual citizenship, and would taking a new nationality cause me to lose an existing one?
3. What duties come with this nationality while living abroad, such as tax filing, registration or military service?
4. If I renounce a nationality, what is the formal process, can it ever be reversed, and which tax filings follow, such as Form 8854 for the United States?
5. How will this nationality interact with my current immigration status and with where I am tax resident?
6. For an investment route, what is the program's legal basis today, has it been changed or challenged, and what due diligence does it apply?
7. Can this nationality pass to my children, including children born abroad, and what registration does that require?

Questions people ask

Where this guide stops

Sources

• Citizenship and NaturalizationOfficial guidance
• Dual citizenshipOfficial guidance
• Give up (renounce) British citizenship or nationalityOfficial guidance
• 8 U.S. Code § 1481 - Loss of nationality by native-born or naturalized citizen; voluntary action; burden of proof; presumptionsPrimary law
• Expatriation taxOfficial guidance
• U.S. citizens and resident aliens abroadOfficial guidance
• Determining an individual's tax residency statusOfficial guidance
• Judgment of the Court (Grand Chamber) of 29 April 2025 – Commission v Malta (Citizenship by investment), Case C-181/23Primary law
• Council Directive 2014/107/EU of 9 December 2014 amending Directive 2011/16/EU as regards mandatory automatic exchange of information in the field of taxationPrimary law
• OECD Model Tax Convention on Income and on Capital: Condensed Version 2017, Article 4 (Resident)Treaty text
• Cabinet Decision No. 85 of 2022 - Unofficial Translation (Federal Tax Authority)Primary law