There is only one file type that uses the .TAX2009 extension:
TurboTax 2009 Tax Return
Tax return created with TurboTax 2009, a United States tax preparation and filing tool; contains 2009 tax forms and data entered by the user; typically edited using the TurboTax's "Interview" mode, but may also be edited by manually entering data into tax forms.
NOTE: TAX2009 files contain Federal and State tax return information for the 2009 tax year. Therefore they are most created and used during the 2010 calendar year.
Updated: May 1, 2010