Who Should Use the Form
There are four conditions that make you eligible to apply for naturalization with Form N-400, any one of which suffices. First, you can be 18 years old or above and a Lawful Permanent Resident for at least five years. If you've only been a Lawful Permanent Resident for three years and are 18 years old, you can apply if you have been married to and living with the same U.S. citizen spouse for at least the past three years. Third, U.S. nationals who are not citizens can apply using Form N-400. Finally, the form can be used by anyone who has served honorably in the U.S. Armed Forces for at least one year, is 18 years old, and a Lawful Permanent Resident, or served in the Selected Reserve or in active-duty status during a designated period of hostilities regardless of residency status.
Completing the Form
The form should be completed in capital letters handwritten in black ink. The 14 different parts gather different kinds of information ranging from criminal records, residence and employment, time outside the U.S., marital history, children, affiliations, and moral character. The Federal Bureau of Investigation uses the information provided in the Form N-400 application, as well as your fingerprints to conduct a thorough background check. The questions are very straightforward, but might require reference to documentation on your part in order to provide the appropriate level of specificity. For example, exact dates of entering and exiting the country, employment or attending schools are requested in parts six and seven.
Those applying based on the continuous residency requirement (five years as a Lawful Permanent Resident, or three years married to a citizen) can file up to 90 days before the date on which they meet these requirements, but must meet all other requirements at the time of filing. The cost of filing Form N-400 varies, but in 2009 the charges rose to $595 plus a biometrics fee of $80 for fingerprinting, making a total cost of $675. Applicants who are 75 years old or older are not charged a biometric fee, and military applicants filing under Section 328 and 329 of the INA are not charged any fee at all. In addition to Form N-400, naturalization applicants must take English language and/or civics tests depending on their age.