Form N-400

#What this actually is

Form N-400 is the application you file with USCIS when you're ready to become a U.S. citizen. It's formally called the "Application for Naturalization," and it's the single form that kicks off the entire citizenship process — from background checks to the civics test to your oath ceremony.

You can file it online or by mail, and as of now the filing fee is $710 (though fee waivers are available if you qualify). Once USCIS receives it, you're officially in the pipeline.

#Who can file

The basic rule: you need to have been a lawful permanent resident (green card holder) for a certain number of years before you're eligible. For most people, that means:

• 5 years as a green card holder (the general rule)
• 3 years if you got your green card through marriage to a U.S. citizen and you're still married and living together

You can actually file up to 90 days before you hit your eligibility date — so don't wait until the exact anniversary. There are also requirements around continuous residence, physical presence, and good moral character, but those are separate from the form itself.

#What happens after you file

The process follows a predictable sequence:

• Receipt notice — USCIS confirms they got your application
• Biometrics appointment — fingerprints and photo at a local USCIS office (sometimes waived if they already have yours on file)
• Interview — an officer reviews your application, asks about your background, and administers the English and civics tests
• Oath ceremony — you take the Oath of Allegiance and officially become a U.S. citizen

Processing times vary by field office, but the whole thing typically takes 8 to 14 months from filing to oath.

#Common issues to watch for

Most N-400 applications are straightforward, but a few things trip people up:

• Travel history gaps — you need to list every trip outside the U.S. for the past 5 years. Keep your passport stamps and travel records.
• Address history — every address for the past 5 years, no gaps. Even short-term stays count.
• Tax issues — if you owe back taxes or didn't file in a year you should have, sort that out before applying. USCIS takes tax compliance seriously.
• Criminal history — even minor offenses like a DUI or shoplifting charge need to be disclosed and can affect your "good moral character" determination.

The form itself asks a lot of yes/no questions about your background. Answer them honestly — USCIS already has much of this information, and inconsistencies cause more problems than the underlying issue ever would.