Publication 559
taxmap/pubs/p559-005.htm#en_us_publink100099815For estate tax purposes, the personal representative may be required to file Form 706, United States Estate (and Generation-Skipping Transfer) Tax Return. If death occurs in 2011, Form 706 must be filed if the gross estate of the decedent is more than
$5,000,000.
Generally, if Form 706 is required, the return is due within 9 months after the date of the decedent’s death. To apply for an automatic 6-month extension of time to file, use Form 4768, Application for Extension of Time To File a Return and/or Pay U.S. Estate (and Generation-Skipping Transfer)
Taxes.
If you believe the estate tax may apply to the decedent's estate, see Publication
950.