For many lawful permanent residents, naturalization represents the final milestone in a long immigration journey. Filing an N-400 — formally known as Form N-400, Application for Naturalization — is how a Green Card holder initiates the process of becoming a U.S. citizen. Understanding who is eligible, what the process involves, and what to expect after filing can help applicants approach this step with greater confidence and fewer surprises.
What Form N-400 is and who files it
Form N-400 is the official application submitted to U.S. Citizenship and Immigration Services (USCIS) by lawful permanent residents seeking to become U.S. citizens through naturalization. It is filed by the applicant directly — not a sponsor or employer — and triggers a review process that includes document verification, background checks, and an in-person interview.
Naturalization through Form N-400 is generally available to Green Card holders who meet the following core eligibility requirements:
- At least 18 years of age at the time of filing
- Lawful permanent resident status
- At least five years of continuous residence in the United States, or three years if the Green Card was obtained through marriage to a U.S. citizen
- Physical presence in the U.S. for at least 30 months out of the required five-year period, or 18 months for marriage-based Green Cards
- Residence for at least three months in the state or territory where the application is filed
- Sufficient English language proficiency to pass a language test, unless an applicable exception applies
- Demonstrated good moral character
- Willingness to take the Oath of Allegiance
Certain military members and veterans may be eligible under different time and residency thresholds.
When to file
USCIS allows applicants to submit Form N-400 up to 90 calendar days before completing the required three- or five-year residency period. Filing early does not accelerate citizenship — the full residency requirement must still be met before naturalization can be granted — but it can provide a practical head start on processing time.
The naturalization process: what to expect
The naturalization process involves several steps that unfold over a period of months. The general sequence frequently observed includes:
- Gathering documentation. Applicants compile supporting materials, which can include evidence of continuous residence, tax records, and other documentation depending on individual circumstances. This step alone can take considerable time.
- Filing Form N-400. The completed form and supporting documents are submitted to USCIS, either online or by mail. Online filing is slightly less expensive and allows for account-based case tracking.
- Biometrics appointment. USCIS schedules an appointment at an Application Support Center to collect fingerprints and a photograph for background and security checks.
- In-person interview. A USCIS officer reviews the application and administers two tests: an English language test and a civics test covering U.S. history and government. Applicants must correctly answer at least 12 out of 20 civics questions during the oral exam.
- Decision. USCIS has 120 days following the interview to issue a decision. In many cases, if both tests are passed, approval is granted on the same day as the interview.
- Naturalization ceremony. Approved applicants receive Form N-445, Notice of Naturalization Oath Ceremony, and attend a ceremony where they return their Permanent Resident Card and take the Oath of Allegiance, at which point they officially become U.S. citizens.
Documents commonly required
While specific documentation requirements vary by individual circumstances, materials frequently submitted with Form N-400 include:
- A photocopy of both sides of the applicant’s Green Card
- Evidence of continuous U.S. residence, such as rent or mortgage statements, pay stubs, or passport entry and exit stamps
- Evidence of good moral character, which may include tax records, court disposition records if applicable, and community involvement documentation
- For marriage-based applicants, a current marriage certificate, evidence of the spouse’s U.S. citizenship, and proof of a bona fide relationship
- For military applicants, applicable discharge or service documentation
- Certified translations for all non-English documents
USCIS may issue a Request for Evidence if additional documentation is needed. Responding promptly and thoroughly is important, as delays in responding can extend processing timelines.
Filing fees and processing times
As of current USCIS guidance, the filing fee for Form N-400 is $710 for online submissions and $760 for paper filings. Fees are subject to change, and applicants should verify current amounts on the USCIS filing fees page before submitting. Fee waivers and reduced fees may be available in certain circumstances, though applicants requesting these must file by mail rather than online.
Processing times vary by field office and individual case complexity. In recent years, average processing times have ranged from approximately five to 13 months depending on location, with a general average frequently cited in the range of eight to 10 months. Any errors, missing documents, or RFEs can add additional time to the process.
The value of legal guidance
While naturalization is a process some applicants navigate independently, the documentation requirements, interview preparation, and potential complications involved mean that working with experienced immigration counsel is frequently cited as a way to reduce the risk of delays or avoidable errors. This is particularly relevant for applicants with complex backgrounds, prior immigration issues, or circumstances that may require additional documentation to demonstrate good moral character.
For Green Card holders who have reached this milestone, the naturalization process is worth approaching with the same level of care and preparation that characterized the earlier steps in their immigration journey.