Form N-600 is used as an application for a Certificate of United States Citizenship. Form N-600 may be used if the applicant can claim U.S. Citizenship either by action of law while residing in the United States or, according to Form N-600, by having been born outside the United States to a parent who is a United States Citizen.

Stepchildren and children who do not regularly reside in the United States may not file Form N-600, but should file Form N-600K, Application for Citizenship and Issuance of Certificate Under Section 322.

Pursuant to Form N-600, a biological child or adopted child of a United States citizen born outside of the United States, and is claiming citizenship by action of law, automatically become a United States citizen if certain criteria are met. The requirement for a Form N-600 applicant includes:

1. He or she has at least one parent who is a United States citizen, whether by birth or naturalization;
2. He or she regularly resides in the United States in the legal and physical custody of the U.S. Citizen parent;
3. He or she has been lawfully admitted for permanent residence;
4. He or she has not yet reached an eighteenth birthday;
5. He or she is a biological child, was legitimate, or was legitimated while in the legal custody of his or her legitimating parent prior to reaching a sixteenth birthday; or
6. Is a biological child born our wedlock and has not been legitimized and the mother of the applicant becomes naturalized as a United States citizen.