The Federal FAFSA form, which is the basic platform on which all financial aid is built, is generally due by the end of June for that school year. For example, the deadline for the 2009-2010 school year will likely be at the end of June 2010.
If you plan on applying for aid from your state, the deadlines are often much earlier in the year. Additionally, the forms for Federal aid do not replace the need to fill out additional state forms.
Lastly, colleges and universities will often have unique deadlines and paperwork requirements for scholarships and programs that are unique to their school. The CSS PROFILE is a separate form used by over 600 schools for private scholarship and aid packages.
To check on the current deadlines, visit the application deadline page of the Department of Educations web page.

