Fill out N-400 (Application for Naturalization) online
Form N-400 is the application for U.S. naturalization (citizenship). Lawful permanent residents who meet the eligibility requirements file this form to become United States citizens, gaining the right to vote, hold a U.S. passport, and petition for family members.
How to fill out N-400 (Application for Naturalization)
Determine eligibility
Confirm you meet the requirements: lawful permanent resident status, required residency period (5 years or 3 years if married to a U.S. citizen), continuous residence, physical presence, good moral character, and English/civics knowledge.
Enter personal information
Provide your full legal name, A-Number, date of birth, country of birth, SSN, current address, and all previous addresses for the last 5 years.
Provide background information
Answer questions about your employment history, marital status, children, travel history outside the U.S., and moral character (criminal history, tax obligations, etc.).
Complete the oath and submit
Affirm your willingness to take the Oath of Allegiance to the United States. Include two passport-style photos, copies of your green card, and the filing fee.
About N-400 (Application for Naturalization)
Who needs this form
Lawful permanent residents (green card holders) who are at least 18 years old and have held their green card for at least 5 years (or 3 years if married to a U.S. citizen). They must have been physically present in the U.S. for at least half of the required residency period.
Where to submit
File with USCIS online at uscis.gov or by mail to the appropriate USCIS lockbox. After filing, attend a biometrics appointment, then an interview with a USCIS officer that includes English and civics tests.
Source and content freshness
- Reviewed: 2026-02-16
- Check the latest official form instructions for the filing year that applies to you.
- Filing deadlines may shift for weekends and holidays. Verify due dates with official instructions.
Common mistakes to avoid
- Filing too early (more than 90 days before meeting the residency requirement)
- Not disclosing all trips outside the U.S. (any trip over 6 months may break continuous residence)
- Failing to register for Selective Service (required for male applicants who were 18-25 while in the U.S.)
- Not preparing for the English and civics test portions of the interview
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What happens at the naturalization interview?
A USCIS officer reviews your N-400 application, verifies your identity, and asks about your background. You will also take an English test (reading, writing, speaking) and a civics test (10 questions from a list of 100 about U.S. history and government; you must answer 6 correctly). If approved, you attend an oath ceremony to officially become a U.S. citizen.
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