The prior edition of the N-400 Application for Naturalization expired on October 31, 2008. A new edition of the form has yet to be posted to the USCIS website. Until further notice, the USCIS has informed the American Immigration Lawyers Association (AILA) that applicants may continue to submit their applications on any useable edition of the form.
To clarify, applicants seeking naturalization may continue to file using Form N-400 found on the USCIS website until a new revised form is posted.