The N-400 is the official application for naturalization within the United States and is an essential part of the naturalization process. This form is filed by permanent residents who seek to apply for United States citizenship. In order to use the N -400 form, the permanent resident must fulfill a variety of different requirements prior to the completion of this form. If incorrect information is provided on the N-400 form, it can end in the denial of the application and even deportation in extreme cases. The N-400 is found in citizenship packages and is mandated by the United States government for the naturalization process. There are certain fees that are associated with the filing of an N-400 form and they vary by situation and lifestyle.