Understanding the purpose of Form N-400 is important for preparing for the naturalization interview. By understanding the form, you will be able to correctly complete the questions and be better prepared for your interview. The immigration officer will use this document to determine your eligibility. You will also need to submit the appropriate supporting documents, such as photocopies of your green card and passport photos. Marriage certificates and death certificates of former spouses are also required. The USCIS website contains a complete list of the documents you must submit with your application. It is important to make sure that you only submit photocopies of the original documents. Before filing Form N-400, you should understand how much it costs. Generally, it costs $725, of which $640 goes to processing the form. The remaining $85 goes towards biometrics services. However, you are exempt from the biometrics fee if you are 75 years or older. If you cannot afford to pay the fee, you can apply for a fee waiver. You can submit your Form N-400 online on the USCIS website or via the postal service. You can also submit it to a USCIS service center in person or through a lockbox. However, foreign applicants and fee-waiver applicants must still use paper forms. You must fill out the form in black ink. If you are submitting it via mail, you should ensure that the mailing address is valid, since postal delivery services vary. To become a naturalized citizen, you must fill out form N-400 and submit it to the U.S. Citizenship and Immigration Services (USCIS). This process can take up to six months and is the first step in the process of naturalization. To begin, you must check whether you are eligible and have a valid green card. If you have a green card and are looking to naturalize, you may be eligible to file N400 Form. In order to do so, you must be married to a U.S. citizen and have lived in the country for at least three years. However, if you are a permanent resident through another category, you will need to wait another five years. You can also file Form N-400 if you already hold a green card and are ready to apply for citizenship.