Form N-400, the Application for Naturalization, is the document you file with USCIS to begin the process of becoming a U.S. citizen. It's a comprehensive form — 20 pages with dozens of questions about your background, immigration history, moral character, and beliefs — and completing it accurately is critical. Errors, omissions, or inconsistencies can delay your case for months or trigger a denial.
This guide walks through everything you need to know about the N-400: who qualifies to file, what documents you need, how to complete the form correctly, what happens after you submit, and how to prepare for the civics test and naturalization interview. Whether you're filing on your own or working with an attorney, understanding the process helps you move through it confidently.
You can only file the N-400 if you meet specific eligibility criteria. The most common path is through continuous residence as a lawful permanent resident (green card holder). The standard requirement is five years of continuous residence in the United States as an LPR, with at least 30 months of physical presence during that five-year period.
If you're married to a U.S. citizen and living with your spouse in a valid marriage, the residence requirement drops to three years — with at least 18 months of physical presence. This is a common path for many applicants.
Beyond the residence requirement, you must meet several other criteria:
You must be at least 18 years old at the time of filing (there are separate paths for children of citizens). You must have good moral character — USCIS looks at your criminal history, tax compliance, selective service registration (for men), and other factors going back at least five years (or three years for the marriage-based path). You must be able to read, write, and speak basic English (with some exceptions for older applicants or those with qualifying disabilities). And you must demonstrate knowledge of U.S. history and government — this is the civics test component.
The N-400 filing package must include specific supporting documents. Missing documents are one of the most common reasons applications are delayed or returned. Here's what you'll typically need:
Copy of your green card (front and back). This proves you're an LPR eligible to apply. If your green card is expired, renew it before filing — or file the N-400 simultaneously with Form I-90 (green card renewal) and explain the situation in your cover letter.
Passport-style photos. USCIS requires two identical photos meeting specific dimensions and background requirements. Check the current USCIS photo specifications before taking your photos.
Filing fee payment. The N-400 has a filing fee (currently $725 for most applicants; $640 if filing online for certain applicants). USCIS periodically adjusts fees — check uscis.gov for the current amount before submitting. Fee waivers are available for qualifying low-income applicants.
Additional documents based on your situation. Depending on your circumstances, you may also need: marriage certificate (if applying through the three-year spouse path), divorce decrees, court records for any arrests or criminal history, military discharge papers, selective service registration, tax returns or IRS transcripts, and evidence of trips outside the U.S. (particularly extended absences).
Organize your documents carefully before filing. USCIS does not return submitted documents — only submit what's required, and keep copies of everything.
The N-400 can be filed online through your USCIS account or by paper. Online filing is generally faster for processing and easier to track. Paper filing is still fully valid and may be preferable if your situation is complex and you want to submit a detailed cover letter and organized document package.
Read every question carefully. The N-400 asks about a wide range of topics, and many questions have nuanced interpretations. For example, questions about criminal history ask about arrests, not just convictions — if you were arrested but not convicted, you still need to disclose it. Questions about organizational memberships and affiliations go back many years and are broadly worded.
When in doubt, disclose. USCIS officers review your case with access to immigration records, FBI background check results, and other government databases. Attempting to hide something that USCIS can find independently is far more damaging to your case than the underlying issue itself. If you have something in your history that concerns you — an old arrest, a gap in tax filing, a prior removal order — consult with an immigration attorney before filing.
Be consistent. If information on your N-400 contradicts information in your immigration file from previous applications, USCIS will flag the discrepancy. Review your prior applications (I-485, I-130, etc.) before completing the N-400 to ensure consistency in names, dates, addresses, and other details.
After USCIS receives and reviews your application, you'll be scheduled for a biometrics appointment (fingerprinting) followed — typically months later — by your naturalization interview. The interview is the centerpiece of the process.
At the interview, a USCIS officer reviews your N-400 with you, asks you to confirm the information on the form under oath, and may ask additional questions about anything that needs clarification. The officer also administers the English and civics tests during this interview.
The English test has three components: reading, writing, and speaking. The reading test requires you to read one of three sentences correctly. The writing test requires you to write one of three dictated sentences. Speaking ability is assessed informally throughout the interview — the officer is evaluating whether you can have a basic conversation in English.
The civics test consists of 10 questions drawn from a list of 100 n 400 citizenship questions that USCIS publishes publicly. You need to answer 6 of the 10 correctly to pass. USCIS makes the 100 questions and their answers freely available — if you study this list thoroughly, the civics test is very manageable. Many applicants use flashcards, practice apps, or study guides to memorize the answers.
Some applicants 65 or older who have been LPRs for 20 or more years qualify for the modified civics test — they only need to study a shorter list of 20 questions. Applicants with qualifying medical disabilities may be eligible for a civics or English test exemption through Form N-648.
If you fail either the English or civics test at your first interview, USCIS will schedule a second examination within 60 to 90 days. Both tests must be passed within two attempts, or your application will be denied.
If the officer approves your case at the interview, you'll receive a notice scheduling your oath ceremony. At the oath ceremony, you take the Oath of Allegiance — the final step that makes you a U.S. citizen. Ceremonies are sometimes held the same day as the interview; more often they're scheduled separately within weeks or months.
At the oath ceremony, you'll surrender your green card and receive a Certificate of Naturalization. This document is your proof of citizenship. Guard it carefully — replacements require filing Form N-565 and paying a fee. Many naturalized citizens request a U.S. passport shortly after their oath ceremony, which provides a second form of citizenship documentation.
The total time from filing to oath ceremony varies significantly. USCIS processing times fluctuate based on the volume of applications and staffing at your local field office. Current processing time estimates are available on the USCIS website by office — check before filing to set realistic expectations. Common timelines range from about eight months to over two years depending on the office.
Working through the N-400 eligibility practice test and common N-400 pitfalls quiz on this site helps you identify gaps in your knowledge before your application and interview. The civics test preparation quiz mirrors the actual 100-question USCIS civics test format.
The civics test is the component most applicants spend the most time preparing for, and rightly so. While the 100 questions are published and the answers are fixed, there are enough questions covering enough different topics that casual preparation often isn't sufficient. You need to actually know the answers, not just recognize them when you see them — the test is oral, and you need to recall answers under pressure.
Flashcards are the most common study tool, and they work well. You can make physical cards or use digital apps. USCIS publishes audio versions of the 100 questions and answers — listening to these during commutes or workouts is an efficient passive study method. Many applicants report that mixing methods (reading, listening, and practice testing) produces faster retention than any single approach.
Pay special attention to the questions with variable answers — specifically the questions about representatives and senators, which require current knowledge. "Who is one of your state's U.S. senators?" depends on your state. "What is the name of the Speaker of the House?" changes with elections. These are questions where a study guide from two years ago might give you an outdated answer. Verify current answers through official sources.
Give yourself at least six to eight weeks of regular practice before your interview. Even 15 to 20 minutes of daily flashcard review is enough to build solid retention if you do it consistently. By the time your interview arrives, you want to be able to answer any of the 100 questions without hesitation — not because you have to answer perfectly, but because confidence in the material makes the entire interview go more smoothly.
The path to U.S. citizenship is long and has real stakes at every step. Understanding Form N-400 thoroughly — and preparing for the civics test and interview with genuine effort — gives you the best possible chance of a smooth, successful naturalization process.