Form N-400 is one of the most important documents you will ever sign. It is the Application for Naturalization — the form that asks the US government to grant you citizenship. It is 20 pages long, contains more than 150 questions, and touches on every major area of your life: where you have lived, who you are married to, every trip you have taken outside the US, and your complete legal and immigration history.

This guide walks you through every section of Form N-400 as it exists in 2026. You will learn what each question really means, which answers trip up applicants, and how to file cleanly so your case moves fast. By the end you will have everything you need to complete and submit your application with confidence.

Before You Start: Are You Eligible?

Before you even open Form N-400, confirm you meet the basic eligibility requirements:

• You are at least 18 years old
• You are a lawful permanent resident (green card holder)
• You have been a permanent resident for at least 5 years (or 3 years if married to a US citizen)
• You have lived in the same state or USCIS district for at least 3 months
• You have been physically present in the US for at least half of the required 5 (or 3) years
• You have maintained continuous residence without trips of 6+ months
• You can read, write, and speak basic English (unless exempt)
• You have knowledge of US history and government
• You are a person of good moral character
• You are attached to the principles of the US Constitution

Part 1: Information About Your Eligibility

Section 1 asks which basis you are applying under. Most applicants check one of:

• Option A: I have been a permanent resident for at least 5 years
• Option B: I have been a permanent resident for at least 3 years and am married to a US citizen
• Option C: I am applying based on qualifying military service

This section also asks whether you are requesting any English or civics exemptions (50/20, 55/15, 65/20, or disability).

Part 2: Information About You

This is the identity section. Enter your:

• Current legal name (exactly as on your green card)
• Name as it appears on your green card (if different)
• Any other names you have used (aliases, maiden name, nicknames used on official documents)
• A-number (from your green card)
• USCIS online account number (if you have one)
• Date of birth
• Country of birth
• Country of citizenship
• Date you became a permanent resident

Part 3: Biographic Information

USCIS asks for your ethnicity, race, height, weight, hair and eye color. These fields are required by federal civil rights data collection rules. Answer honestly; there are no “wrong” answers.

Part 4: Contact Information

Provide your home phone, mobile phone, and email. USCIS may contact you by email for interview scheduling and updates. Use an email you check daily.

Part 5: Residence History (Past 5 Years)

List every address you have lived at for the past 5 years (or 3 years if applying based on marriage). Include:

• Street address, city, state, ZIP
• Dates you lived there (month and year)
• No gaps — the dates must be continuous

If you have moved often, use Part 12 to list additional addresses. Missing a single address will trigger an RFE.

Part 6: Marital History

This section asks about your current marriage and every previous marriage:

• Current spouse: full name, date of birth, address, immigration status, date of marriage
• Number of prior marriages and how each ended (divorce, death, annulment)
• If applying under Option B (3-year rule): your spouse must be a US citizen for all 3 of those years, and you must prove the marriage is real

Applicants under Option B should bring proof of a bona fide marriage to the interview: joint tax returns, joint bank statements, joint lease, utility bills in both names, photos, and birth certificates of any children.

Part 7: Information About Your Children

List all of your children — biological, step-children, adopted, deceased, married, unmarried, living with you or not. USCIS wants a complete family tree. For each child, provide:

• Full name
• Date of birth
• Country of birth
• A-number (if applicable)
• Current address

Part 8: Employment and School History (Past 5 Years)

List every employer and every school you attended full-time in the past 5 years. Continuous dates required — no gaps. If you were unemployed, list “Unemployed” with dates. If you were a stay-at-home parent, list “Homemaker.”

Part 9: Time Outside the United States (Past 5 Years)

This is the trickiest and most important section. You must list every single trip out of the US in the past 5 years, even day trips. For each trip:

• Date you left the US
• Date you returned
• Country/countries visited
• Total days out of the US for that trip

USCIS will verify your answers against CBP records. If you forget a trip, it may look like deception. Be thorough.

Part 10: Additional Information (The Yes/No Questions)

This is the longest and most important part of N-400 — dozens of yes/no questions about your moral character, criminal history, affiliations, tax compliance, and more. Sample questions include:

• Have you ever been arrested, cited, or detained by any law enforcement officer for any reason?
• Have you ever committed a crime or offense for which you were not arrested?
• Have you ever been a member of the Communist Party or any terrorist organization?
• Have you ever failed to file a required tax return?
• Do you owe any overdue federal, state, or local taxes?
• Have you ever lied to a US government official to obtain an immigration benefit?
• Have you ever failed to support your dependents or pay alimony?
• Have you ever been arrested for, charged with, or convicted of any crime?
• Have you ever helped anyone enter or try to enter the US illegally?
• Are you a male who has registered with Selective Service?

Part 11: Attestation and Signature

You sign under penalty of perjury that all answers are true. If you are filing online, you sign electronically. If paper, sign in blue or black ink.

Part 12: Additional Information for Answers

Use this section to elaborate on any “yes” answers in Part 10, explain gaps in residence or employment, and disclose aliases. Longer is better than shorter — over-explain rather than under-explain.

Filing Fees and Payment

Pay by credit card online, or by check, money order, or Form G-1450 (credit card authorization) if paper filing. Fee waivers available via Form I-912 for low-income applicants.

Supporting Documents to Include

• Copy of both sides of your green card
• Two passport-style photos (only if filing from outside the US; not needed for domestic filings)
• Marriage certificate (if applying under the 3-year rule)
• Divorce decrees for all prior marriages (both you and your spouse)
• Proof of spouse’s US citizenship (if 3-year rule)
• 3 most recent years of tax returns (if 3-year rule) or 5 years (if 5-year rule)
• Court records for any arrests, charges, or convictions
• Selective Service registration proof (if male who lived in US between 18–26)

Online Filing vs Paper Filing

Common N-400 Mistakes to Avoid

1. Listing the wrong date for your green card. Use the “Resident Since” date on your card, not the issue date.
2. Forgetting a short trip abroad. Even a weekend in Canada counts.
3. Answering “no” to arrests when you were arrested years ago. USCIS will find it.
4. Not disclosing name changes. Every variation must be listed.
5. Wrong answer to Selective Service. Men who lived in the US between 18 and 26 must register, even if only temporarily.
6. Incorrect filing fee amount. Triple-check the current fee at uscis.gov before mailing.
7. Missing signature. One unsigned form = automatic rejection.
8. Using pencil or erasable ink. Black or blue ink only on paper forms.

Frequently Asked Questions

Final Word

Form N-400 looks long and intimidating, but every section is logical and every question has a clear correct answer — if you tell the truth and take your time. The most successful applicants are not the ones with the perfect histories; they are the ones who prepare carefully, disclose everything, and show up organized. Start the form today. In less than a year, you could be standing in a federal courthouse, raising your right hand, taking the Oath of Allegiance.