If you are not a U.S. citizen by birth or did not acquire/derive U.S. citizenship automatically after birth, you may still be eligible to become a citizen through the naturalization process. Eligible persons use the Application for Naturalization (Form N-400) to apply for naturalization.
You become a citizen as soon as you take the Oath of Allegiance to the United States in a formal naturalization ceremony. USCIS will notify you of the ceremony date with a Notice of Naturalization Oath Ceremony (Form N-445).
In many cases, you may reapply. If you reapply, you will need to complete and resubmit a new Form N-400 and pay the fee again. You will also need to have your biometrics taken again. If your application is denied, the denial letter should indicate the date you may reapply for citizenship. If you are denied because you failed the English or civics test, you may reapply for naturalization as soon as you want. You should reapply whenever you believe you have learned enough English or civics to pass both tests.
You may get a new Certificate of Naturalization by submitting an Application for Replacement Naturalization/Citizenship Document (Form N-565) to USCIS.
To be eligible for naturalization you must be a person of good moral character. Committing certain crimes may cause you to be ineligible for naturalization (USCIS calls these bars to naturalization). When determining if an applicant has good moral character, USCIS considers such things as honesty and criminal records. Please note that if you have committed certain serious crimes, USCIS may decide to remove you from the United States. If you have questions, you may want to seek advice from an immigration attorney before applying.