N-400 Citizenship Form: Complete Application Guide 2026

What Is the N-400 Citizenship Form?

The N-400 is the official Application for Naturalization — the form you file with USCIS when you want to become a U.S. citizen. It's one of the most significant government forms you'll ever complete, and getting it right the first time matters. Errors, omissions, or inconsistencies can delay your application by months or result in a Request for Evidence (RFE) that adds time and stress to an already lengthy process.

The N-400 is administered by U.S. Citizenship and Immigration Services (USCIS) and can be filed online through a USCIS online account or by mail to the appropriate USCIS lockbox facility. The form collects your personal information, immigration history, background, and information about your moral character — and you'll answer every question under penalty of perjury.

This guide walks you through what the N-400 covers, how to complete it accurately, what documents you need, and what happens after you submit.

Who Can File the N-400?

To file the N-400, you must meet specific eligibility requirements. The most common path is naturalization based on five years of permanent residency (or three years if you obtained your green card through marriage to a U.S. citizen and have been married to and living with that citizen for three years).

General eligibility requirements include:

• You are at least 18 years old
• You are a lawful permanent resident (green card holder)
• You have lived in the U.S. as a permanent resident for at least 5 years (or 3 years under the marriage exception)
• You have been physically present in the U.S. for at least 30 months out of the last 5 years (or 18 months out of the last 3 years under the marriage exception)
• You have lived in the state or USCIS district where you're applying for at least 3 months
• You have good moral character
• You can read, write, and speak basic English (exceptions apply for certain age/residency combinations)
• You can pass the civics test

There are special naturalization paths for military members, certain spouses of U.S. citizens stationed abroad, and children of U.S. citizens. If your situation is complex, consult an immigration attorney before filing.

Documents You'll Need

Gather these before you start filling out the form:

• Green card (front and back copy) — required for all applicants
• Passport photos — two identical photos meeting USCIS specifications
• Passport or travel document copies — pages showing travel outside the U.S. in the last 5 years
• Tax returns or IRS transcripts — for the last 5 years if required to file
• Marriage certificate — if filing under the 3-year marriage exception or if you've been married
• Divorce decrees — for any previous marriages
• Evidence of name change — if your name has changed and you want it reflected on your naturalization certificate
• Military service records — if applicable

Additional documents may be required based on your answers to specific N-400 questions — for example, arrest records, court documents, or explanation letters for certain yes/no answers. Be honest in your responses; USCIS can and does check.

How to Complete the N-400: Section by Section

The N-400 has 18 parts. Here's what each covers:

Parts 1–3: Your Background

Basic information — your name, other names used, USCIS online account number, and Alien Registration Number (A-Number). Your A-Number appears on your green card and is crucial — don't leave it blank or enter it incorrectly. Parts 1–3 also ask for contact information, Social Security number, and whether you want a disability accommodation for your interview.

Parts 4–6: Residence, Employment, and Travel

You'll list your addresses for the past 5 years, your employers for the past 5 years, and all travel outside the U.S. during the past 5 years. Be thorough — USCIS cross-references this information with passport records and other databases. Missing trips, especially longer ones, is a common error that triggers RFEs.

For travel, list the destination country, departure date, return date, and purpose for every trip. If you took many short trips, make sure you account for all of them. If you're unsure of exact dates, check your passport stamps and any travel records you have.

Part 7: Marital History

List your current marital status and all previous marriages — even those that ended in divorce or death of a spouse. Include the name of each former spouse, how and when the marriage ended, and documentation details. Omitting a previous marriage is one of the most common causes of serious application problems.

Part 8: Children

List all your biological, adopted, and stepchildren regardless of their age, citizenship status, or where they live. You'll need each child's name, date of birth, and country of birth.

Parts 9–12: Additional Information

These sections cover your organization memberships, tax compliance, prior removal proceedings, prior applications for immigration benefits, and military history. Answer carefully and honestly — many of these questions are designed to uncover potential bars to naturalization or issues with good moral character.

Parts 13–16: Good Moral Character

This is the longest and most scrutinized section. You'll answer yes/no questions about criminal history, arrests, citations, affiliations with organizations that oppose the U.S. government, gambling offenses, alcohol-related incidents, and more. Answer every question truthfully. A yes answer doesn't automatically bar you from citizenship — USCIS evaluates context — but a false answer (lying about criminal history, for example) is grounds for denial and potentially criminal charges.

If you have any arrest, citation, or court record — even one that was dismissed or expunged — disclose it and attach documentation. Omitting it is far more damaging than disclosing it.

Parts 17–18: Oath and Signature

The final sections include attestation questions (confirming your willingness to take the Oath of Allegiance, bear arms for the U.S., perform noncombatant service, etc.) and your signature. Sign and date every required signature line. Missing a signature is a simple but common error that causes applications to be rejected and returned.

Filing Online vs. By Mail

USCIS allows you to file the N-400 online through a USCIS online account or by paper mail. Online filing has advantages: you can save your progress, receive electronic status updates, and avoid common mail-related issues like missing documents. Most applicants find the online system more convenient.

If you file by mail, follow the N-400 instructions precisely for document assembly and mailing address. Addresses vary by state and whether you qualify for the reduced fee or fee waiver. Using the wrong address can delay processing significantly.

Fees and Fee Waivers

The standard N-400 filing fee is $760 (includes biometrics). A reduced fee of $460 is available for applicants whose household income falls between 150% and 400% of the Federal Poverty Guidelines. A full fee waiver (Form I-912) is available for applicants at or below 150% FPG or those receiving certain means-tested public benefits.

If you're requesting a fee waiver, file Form I-912 with your N-400 and include supporting documentation. USCIS processes these together — don't submit them separately.

What Happens After You Submit

Here's the general sequence after USCIS receives your N-400:

1. Receipt Notice: USCIS sends a Form I-797 receipt notice confirming they've received your application. Keep this — it contains your receipt number for tracking.

2. Biometrics Appointment: USCIS schedules you for a biometrics appointment at an Application Support Center (ASC) near you. You'll be fingerprinted and photographed. Bring your appointment notice and government-issued photo ID.

3. Background Check: USCIS runs background checks using your biometrics and the information in your application. This process runs concurrently with other application steps.

4. Interview Notice: USCIS schedules a naturalization interview at your local field office. Prepare thoroughly — the officer will test your English and civics knowledge at the interview.

5. Naturalization Interview: You'll meet with a USCIS officer who reviews your application, asks about your background, tests your English, and administers the civics test (up to 10 of the 100 official civics questions; you must answer 6 correctly). Bring original documents for anything USCIS asked you to bring.

6. Decision: USCIS can grant your application at the interview, continue it pending additional review, or deny it. Most applicants receive a decision at or shortly after the interview.

7. Oath Ceremony: If approved, you'll attend a naturalization ceremony where you take the Oath of Allegiance and receive your Certificate of Naturalization. This is the final step — you're officially a U.S. citizen.

Common Mistakes to Avoid

These errors trip up many applicants:

• Missing travel entries: Document every trip outside the U.S. in the last 5 years, no matter how short.
• Omitting past marriages: List all marriages, including brief ones that ended long ago.
• Leaving blanks instead of writing "N/A": Every question must be answered — use "N/A" for not applicable, never leave it blank.
• Wrong fee or missing signatures: Double-check fee amount and sign every required line before submitting.
• Not preparing for the civics test: The interview comes faster than most people expect. Start studying the 100 civics questions early.

Preparing for the Civics Test

The naturalization interview includes a civics test covering U.S. history and government. USCIS provides the official list of 100 civics questions on their website — the officer will ask you up to 10 randomly selected questions from that list, and you need to answer 6 correctly to pass.

The questions range from foundational facts (how many senators does each state have? what is the supreme law of the land?) to slightly more nuanced history and government questions. Most people find that consistent practice with the full list of 100 questions — not just passive reading, but active recall — is the most effective prep approach. Use practice tests to build the retrieval fluency you'll need when answering questions face-to-face with an officer.

Start preparing for the civics test as soon as you file your N-400 — don't wait for the interview notice. Processing times vary, and interviews can come sooner than expected.