How to file Form N-400 (Application for Naturalization)
Form N-400, Application for Naturalization, is the USCIS form a lawful permanent resident files to apply for U.S. citizenship. This page describes the general process — the form, the fee, the filing channels, and the steps that follow — with every factual claim cited to a primary source. It describes the process in general terms only; it is not advice about any individual case.
What Form N-400 is
Form N-400 is the application for naturalization — the process by which a lawful permanent resident becomes a U.S. citizen. USCIS publishes the current form edition, its instructions, and the filing options on the official N-400 page, and the instructions are the controlling reference for how the form itself must be completed.
The general eligibility requirements
In general, an applicant must be at least 18 years old and must have been a lawful permanent resident for at least 5 years. Certain applicants who are married to and living with a U.S. citizen may apply under a separate 3-year provision.
The requirements also generally include at least 30 months of physical presence in the United States within the qualifying period, and at least 3 months of residence in the state or USCIS district where the application is filed.
The remaining general requirements are continuous residence for the qualifying period, good moral character, the ability to read, write, and speak basic English, knowledge of U.S. history and government (civics), and attachment to the principles of the Constitution. Each requirement has exceptions and accommodations that USCIS describes in its Policy Manual — age- and disability-based test exemptions among them.
Special naturalization provisions apply to certain current and former members of the U.S. armed forces.
When the application can be filed
USCIS permits filing Form N-400 up to 90 days before the continuous-residence requirement is complete. The N-400 instructions state the exact early-filing rule, and the other requirements must still be met at filing.
The filing fee
Under the current USCIS fee schedule (Form G-1055), the N-400 filing fee in the general category is $760 for a paper filing or $710 for an online filing.
A reduced fee of $380 applies to applicants who document household income at or below 400% of the Federal Poverty Guidelines; the reduced-fee filing is paper only. There is no filing fee for applicants filing under the military provisions.
There is no separate biometric services fee for Form N-400 — since the 2024 fee rule, biometrics costs are included in the filing fee.
Filing online or by mail
Form N-400 can be filed online through a USCIS online account or on paper by mail. A paper filing goes to the address in the USCIS direct filing address chart, which depends on the filing category and location — the chart on USCIS.gov is the current reference.
An application filed with a fee-waiver or reduced-fee request cannot be filed online; those filings are paper only.
What happens after filing
After the application is received, USCIS issues Form I-797C, Notice of Action, as the receipt. USCIS may reuse previously submitted biometrics or schedule a biometric services appointment.
Case status can be checked online using the receipt number. Processing times vary by field office; USCIS publishes current estimates in its processing-times tool, and this page does not claim any specific timeframe.
The interview and the tests
USCIS schedules an interview on the application. At the interview, an officer tests English reading, writing, and speaking, and knowledge of U.S. history and government (civics). Exemptions and accommodations exist for certain applicants, and USCIS publishes free official study materials for both tests.
The oath ceremony
An applicant whose application is approved becomes a U.S. citizen upon taking the Oath of Allegiance at a naturalization ceremony. The Certificate of Naturalization is issued at the ceremony, and USCIS describes how ceremonies are scheduled.
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How much does Form N-400 cost?
Under the current G-1055 fee schedule, the general-category filing fee is $760 on paper or $710 online. A documented reduced fee of $380 (paper only) and a $0 military-provision category also exist.
Can Form N-400 be filed online?
Yes — through a USCIS online account. The exception: an application filed with a fee-waiver or reduced-fee request cannot be filed online and must be mailed.
How early can Form N-400 be filed?
USCIS permits filing up to 90 days before the continuous-residence requirement is complete; the N-400 instructions state the exact rule.
What is on the naturalization test?
An English test (reading, writing, speaking) and a civics test on U.S. history and government, given at the interview. Exemptions and accommodations exist, and USCIS publishes free study materials.
When does an applicant become a U.S. citizen?
Upon taking the Oath of Allegiance at a naturalization ceremony, after the application is approved. The Certificate of Naturalization is issued at the ceremony.