Form N-400, Application for Naturalization, is the official form used by permanent residents (green card holders) to apply for U.S. citizenship through the naturalization process.

The N-400 application is submitted by green card holders who wish to become U.S. citizens. It collects information about the applicant’s background, residence, and eligibility for naturalization, including continuous residence and good moral character.

Form N-400 is used to apply for U.S. citizenship through naturalization. Eligible applicants must meet certain requirements, such as having a green card for at least 3 or 5 years, depending on their case, and demonstrating knowledge of U.S. history, government, and the English language.