The short version
Under section 320 of the Immigration and Nationality Act (INA), as changed by the Child Citizenship Act of 2000, a child born outside the United States automatically becomes a U.S. citizen when all of these are true at the same time, before the child's 18th birthday:
- At least one parent is a U.S. citizen, by birth or by naturalization (an adoptive parent counts).
- The child is under 18.
- The child is a lawful permanent resident (has a green card).
- The child is living in the United States in the legal and physical custody of the U.S. citizen parent.
There's no application to become a citizen this way and no separate oath. The child simply is a citizen from the date the last condition was met. Filing Form N-600 later is only a request for a document that proves it.
The conditions, one at a time
A U.S. citizen parent
For most readers of this site, this is the day you take the Oath of Allegiance: you become a citizen when you take the oath at the ceremony, not at the interview (see what happens after the interview). Only one parent needs to be a citizen. USCIS must also recognize the parent-child relationship. The N-600 instructions list biological children (if the citizen parent is the biological father, the child generally must have been born in wedlock or legitimated), adopted children, and certain children born through assisted reproduction where the citizen parent is a legal parent.
Stepchildren are not covered. The instructions say plainly that a stepchild cannot acquire citizenship this way unless the stepparent adopts them.
Under 18
All the conditions must come together before the 18th birthday. The Policy Manual treats a child whose last condition is met on the 18th birthday itself as still under 18. After that, INA 320 no longer applies; an adult child who has a green card would generally need to qualify for naturalization on their own.
A green card
The child must be a lawful permanent resident. Living in the United States on a visitor, student or other temporary status doesn't meet this condition, even if the parent is a citizen. The conditions can be met in any order, so a child who gets a green card after the parent naturalizes can still qualify, as long as everything lines up before age 18.
Living in the U.S. in the citizen parent's custody
This has two parts.
- Physical custody means the child actually lives with the U.S. citizen parent. The Policy Manual defines residence as the child's "principal, actual dwelling place." Records with matching addresses, such as school and medical records, can show this.
- Legal custody is usually simple. Parents named on the birth certificate are generally presumed to have it, and married parents living together are presumed to share it. It gets more complicated after a divorce or separation: a court's custody order controls, and a private agreement between parents generally does not override it. Joint custody awarded by a court counts; sole custody isn't required. A custody order entered after the child turned 18 that tries to apply backward is not recognized.
If the parents never married, the parent the child lives with is generally presumed to have legal custody. Where that parent is the father, he must also have legitimated the child under the law of the child's or the father's residence.
Situations that need a closer look
- Adopted children. They qualify through an adoptive U.S. citizen parent if the adoption meets the definitions in immigration law. Children who enter the U.S. on an IR-3 or IH-3 visa and meet INA 320 receive a Certificate of Citizenship automatically, without filing Form N-600. For other adoptions, see uscis.gov/adoption.
- Children who live abroad. INA 320 requires living in the United States. A child under 18 who regularly lives outside the U.S. may instead qualify under INA 322, which is a different process with its own form, Form N-600K.
- Military and government families. Since a 2020 law, a child of a U.S. armed forces member or U.S. government employee (or certain spouses) who is stationed abroad can meet the residence condition while living with that parent outside the U.S., under INA 320(c).
- Older cases. The current rules apply to children who were under 18 on February 27, 2001, or born after it. For someone who was already 18 by then, older laws apply, and the Policy Manual covers them separately.
If any of these, or a divorce, custody dispute or out-of-wedlock birth, applies to your family, talk to an immigration attorney or a DOJ-accredited representative before filing.
Getting proof: Form N-600 or a U.S. passport
Because citizenship under INA 320 is automatic, the law doesn't require you to get any document. In practice, your child will need proof of citizenship for things like school, jobs and travel. USCIS names two options:
- A Certificate of Citizenship from USCIS, by filing Form N-600.
- A U.S. passport from the Department of State. The Policy Manual accepts a valid, unexpired U.S. passport as evidence of citizenship. For passport rules, including what a child's application needs, check travel.state.gov.
You can file Form N-600 at any time, even years later, and an adult who became a citizen this way as a child can file it for themselves. A parent or legal guardian files it for a child under 18.
What the N-600 asks for
The instructions (edition 01/20/25) list the evidence. For a child claiming citizenship through a naturalized parent, that usually means copies of:
- The child's birth certificate, issued by a civil authority.
- The parent's proof of citizenship, such as the Certificate of Naturalization.
- The parents' marriage certificate, and divorce decrees or death certificates for any earlier marriages.
- The child's green card.
- Proof of legal custody if the parents divorced or separated, or if the child was adopted or legitimated, plus the adoption decree or legitimation documents if they apply.
- Evidence of any legal name change.
Documents in another language need a full certified English translation. If a required document doesn't exist, the instructions explain what secondary evidence (such as school or baptismal records) you can send instead.
Fee and filing
According to the USCIS fee schedule (Form G-1055, edition 10/16/26), Form N-600 costs $1,335 online or $1,385 on paper. It's $0 for a child adopted under certain immigration-law definitions, and for a current or former member of the U.S. armed forces requesting a certificate for themselves (children of service members don't get this exemption). A fee waiver with Form I-912 is possible if you qualify. Fees change, so check the amount on the N-600 page before you pay.
You can file online with a USCIS account, except if you're applying from outside the U.S., requesting a fee waiver, or are a military member or veteran filing for yourself; those applications go by mail. Use the current edition of the form, check only one box in each Part 1 question, and sign it. A parent or guardian signs for a child under 14. USCIS rejects unsigned forms.
After you file
- Biometrics. USCIS may schedule an appointment for fingerprints, a photo and a signature.
- Interview. USCIS can decide the case without an interview if the file already proves the claim, for example with the parent's Certificate of Naturalization. If you're called in, a parent or legal guardian must come and testify for a child under 18.
- Oath. Children 14 and older take the Oath of Allegiance; USCIS waives it for children under 14. (Read the oath and what it means in our Oath of Allegiance guide.)
- Certificate. If approved, USCIS issues a Certificate of Citizenship showing the date the child became a citizen: the date the last condition was met.
Don't file a second N-600 if one was already decided; USCIS rejects it. To replace a lost or stolen certificate, the form is N-565, not N-600.
If you're still on the way to citizenship
Everything above starts with your own naturalization. Find your earliest filing date with the citizenship date calculator, read the part-by-part N-400 walkthrough, and start studying with the civics practice test.
Sources: USCIS Policy Manual, Vol. 12, Part H, Chapter 4 (Automatic Acquisition of Citizenship after Birth, INA 320); USCIS: Form N-600 and the Form N-600 Instructions (edition 01/20/25); USCIS: Form N-600K; USCIS Form G-1055, Fee Schedule (edition 10/16/26); 8 CFR 341.2 (interviews). This is general information, not legal advice.