If you were an employee and received wages subject to U.S. income tax withholding, you must file Form 1040NR-EZ by April 15th, 2010.
If you have filed an extension before April 15th for Form 1040 NR-EZ, the next deadline for Form 1040NR-EZ is October 15th, 2010.
Extension of Time to File Form 1040 NR-EZ
If you can't file your Form 1040NR-EZ by the due date, you should file Form 4868 to receive an extension of time. You must file Form 4868 by the regular due date of the return.
Please note that Form 4868 does not extend the time to pay your income tax, the tax is still due by the regular due date of the return.