The N 400 form is the document to petition naturalization. If an individual is already a permanent resident and has lived in the United States for a minimum of five consecutive years, then they may begin the naturalization process by completing an N 400 form. This is a very important form as it establishes residency, shows the patterns and background of the individual as they have lived within the United States, as well as the employment and personal background. An N 400 form must be filled out truthfully as it will be referred to often in the process of naturalization. If approved, naturalization will be theirs and this individual will become a citizen of the United States.