When is the last filing date for 2009 tax return in usa?

To pay any income tax that may been due April 15, 2010. If you are due a refund October 15, 2010.

Your Q isn't as clear as you may think. If your asking how long does somebody have to fie a return for 2009 till it is no longer needed - the answer is forever. You must file the return by April 15th of the next tax year (1010) and will always be responsible for it from that point on. Extensions for 6 months are easy to obtain, but one must file a form to do so.

NOTE: This is for filing the forms...paying the tax there is no extension for and it is paid through the year 2009 (by withholding or estimated qrtly payment) and proven (additional paid/overpaid refunded) with the April 15th filing of the form