Converting legal permanent residency into citizenship requires first that the applicant qualify. Qualifications include the amount of time spent living as a permanent resident in the U.S., the applicant's record of international travel while living as a permanent resident and proof of good moral character. Once a green card holder qualifies for citizenship, the application is procedural and concludes with an in-person interview. Converting a green card into citizenship allows the new US citizen to travel freely, vote and have access to federal grants and funding.
Complete your residency period. In order to naturalize, a legal permanent resident (green card holder) must live continuously in the US for five years. (Permanent residents whose green cards are based on marriage to a US citizen are only required to complete a residency period of three years before applying for citizenship.) During the residency period, you cannot leave the U.S. for a period exceeding one year without obtaining both a reentry permit and N-470 Application to Preserve Residence for Naturalization purposes.
Download, print and complete Form N-400 from the website of the United States Citizenship and Immigration Services, uscis.gov. On the top right-hand corner of every page, write your A-Number, which appears on your green card.
Compile the supporting evidence, including a color photocopy of the front and back of your green card as well as two identical passport-style photos. Additional supporting evidence is required based on your individual case. Depending on the circumstances surrounding your immigration, you may be required to submit marriage or birth certificates, police reports, tax or travel documents, military forms or other items. To find out which documents pertain to your individual case, refer to the N-400 document checklist available at the USCIS website.
Submit the N-400 application form along with the supporting evidence and filing fee to the appropriate USCIS filing center. The application fee, including the biometrics fingerprint scan, is $680 as of January 2011, and must be paid in the form of check or money order written to the US Department of Homeland Security. You must send the application to the filing center that services your state of residence. To find out the appropriate address, refer to the "Where to File" section of the N-400 forms page on the USCIS website.
Attend a scheduled interview with an USCIS officer. Once your application is reviewed and approved you will be notified by the USCIS to schedule a citizenship interview. During the interview you must submit a digital fingerprint scan and pass tests in both the English language and U.S. civics. The exams are given during the course of the interview.
Attend the citizenship ceremony. If you pass the interview, you will be notified by mail as to where and when to attend a citizenship ceremony. The ceremony is not optional, all naturalized citizens must attend and swear allegiance to the flag in front of a justice of the peace. Following the ceremony, you will receive your certificate of citizenship.