Form N-400 vs. Form N-600: Which Citizenship Form Should You File?

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If you were born outside the United States to parents who were already U.S. citizens, you may already be a U.S. citizen and not realize it. If you were born outside the United States to parents who became citizens after you, you may have acquired or “derived” citizenship without ever filing anything. And if you are a lawful permanent resident who has lived in the U.S. long enough, you may be ready to apply for citizenship through naturalization.

Three different paths, three different forms, three different processes. Choosing the wrong one wastes time and filing fees and can delay your case for years. Below is how Passage Immigration Law explains the difference to clients, and the questions we walk through before recommending a form.

The two forms most people confuse: Form N-400 vs. Form N-600

Most of the confusion lands on these two USCIS forms. They sound similar, sit in the same part of the USCIS website, and both deal with citizenship. They do very different things.

Form N-400, Application for Naturalization

Form N-400 is for lawful permanent residents (green card holders) who want to become U.S. citizens. The applicant is not yet a citizen and is asking USCIS to grant citizenship through naturalization. The applicant must meet residence, physical presence, and good moral character requirements, take an English and civics test in most cases, and attend an oath ceremony.

If you are filing N-400, USCIS is going to look closely at your time inside and outside the United States, your tax filings, any arrests or citations, and your continuous residence. Our internal pre-filing review covers all of these areas before we file, because surprises at the interview cost time and sometimes the case.

Form N-600, Application for Certificate of Citizenship

Form N-600 is for people who are already U.S. citizens but need an official document proving it. They became citizens automatically — at birth abroad to U.S. citizen parents, or by deriving citizenship through a parent’s naturalization while they were a minor lawful permanent resident — but they don’t have a U.S. passport or other proof. The N-600 produces a Certificate of Citizenship.

This is not an application to become a citizen. It is an application for proof. There is no English test, no civics test, and no oath ceremony — because USCIS is recognizing citizenship the person already has.

How to tell which one applies to you

The simplest test is this: was at least one parent a U.S. citizen at the time of your birth, or did a parent become a citizen while you were under 18 and a green card holder? If yes, N-600 is likely your form. If no, and you have a green card and want to become a citizen, N-400 is your form.

It gets more nuanced fast, especially when:

• The U.S. citizen parent was the father, the parents were not married, and there is a question about legitimation or acknowledgment.
• The U.S. citizen parent had not lived in the United States long enough before the child’s birth to “transmit” citizenship under the law in effect when the child was born.
• The child became a lawful permanent resident before age 18, and the parent naturalized while the child was still a minor — the dates and residency requirements of the Child Citizenship Act of 2000 control whether citizenship was acquired automatically.
• The applicant is adopted.

The rules that decide acquired or derived citizenship change based on the year the applicant was born and the year the parent naturalized. Two siblings can be born to the same parents and only one of them be a U.S. citizen at birth, depending on the dates and residency periods. This is why we open every citizenship case with a careful timeline review before deciding which form to file.

What about a U.S. passport application instead of N-600?

A U.S. passport is one of the easiest ways to prove citizenship for someone who acquired it at birth, and it is often faster and less expensive than filing N-600. For travel purposes, a passport is enough. For Social Security, certain federal benefits, or high-trust employment that requires a Certificate of Citizenship specifically, the N-600 is still the right route. We sometimes recommend pursuing both — applying for the passport first to establish citizenship through the State Department, then filing N-600 if the client wants the formal certificate as well.

Common mistakes we see when people choose the wrong form

• Filing N-400 when the applicant is already a citizen. A green card holder who is in fact a U.S. citizen by derivation should not be filing N-400. USCIS will adjudicate it as a naturalization, but the test, oath, and process are unnecessary, and the filing fee is wasted.
• Filing N-600 without verifying the parent’s qualifying U.S. residence. If the U.S. citizen parent did not meet the physical presence requirement that applied when the child was born, citizenship was not transmitted at birth. Filing N-600 without that proof will lead to a denial and a much harder fix.
• Treating N-600 like N-400. Some clients arrive ready to study for the civics test for an N-600 application. There is no test for N-600. The application is a documentary review.
• Missing the deadline for derivation. Derivation under the Child Citizenship Act requires the child to be under 18 and a lawful permanent resident living in the legal and physical custody of the U.S. citizen parent at the moment the parent naturalizes. Once the child turns 18, derivation is closed and N-400 becomes the only path.

The 2026 filing fees

Filing fees change. As of 2026, the fees are listed on the USCIS website, and any guide should be checked against the most recent fee schedule before filing. We update our intake materials whenever USCIS publishes a new fee schedule.

Free download: Citizenship Guide and Document Checklist

How Passage Immigration Law approaches citizenship cases

Every citizenship case at our firm starts the same way: a timeline review. We map the parents’ citizenship history, the client’s residence and travel, marriages and divorces, any criminal contacts, and tax history. Once that timeline is on paper, the right form usually picks itself. From there we prepare the application, the supporting evidence, and the interview prep so the client walks in confident.

If you are not sure whether to file N-400, N-600, or simply apply for a U.S. passport, the safest first step is a consultation. We have helped clients confirm citizenship they did not know they already had, and we have helped lawful permanent residents through the full naturalization process.

Related reading

• Citizenship and Naturalization Services
• Good Moral Character and Naturalization
• Am I Already a Citizen Even Though I Was Born Outside the U.S.?
• The Nine Standard Eligibility Requirements to Become a U.S. Citizen

This article is general legal information and not legal advice. Citizenship cases turn on dates and facts that vary case to case. If you are evaluating a citizenship application, schedule a consultation with Passage Immigration Law so we can review your timeline and make a specific recommendation.