Form N-400 and US Naturalization

How naturalization through Form N-400 works

Form N-400 is the application a lawful permanent resident files with USCIS to become a US citizen through naturalization. Most applicants qualify after five years as a green card holder, or after three years if they have been married to and living with a US citizen spouse during that time. The statutory period also requires continuous residence, physical presence in the United States for at least half of it, and good moral character.

After filing, USCIS collects biometrics and schedules an interview, where an officer reviews the application under oath and gives the English and civics tests. Applicants with a qualifying physical or mental impairment can seek an exception to those tests through Form N-648, certified by a licensed medical professional. Citizenship takes effect only once the applicant takes the Oath of Allegiance at a ceremony, not when the interview is passed.

A denied applicant can ask USCIS for an administrative hearing on Form N-336 and, if that fails, seek review in federal district court. N-400 is often confused with Form N-600, which documents citizenship already acquired through a parent rather than granting it.