In addition to the 6-month extension, taxpayers who are out of the country (as defined in he form 4868 instructions) can request a discretionary 2-month additional extension of time to file their returns (to December 15 for calendar year taxpayers). To request this extension, you must send the IRS a letter explaining the reasons why you need the additional 2 months. Send the letter by the extended due date (October 15 for calendar year taxpayers) to the following address:
Department of the Treasury
Internal Revenue Service Center
Austin, TX 73301-0215
You will not receive any notification from the IRS unless your request is denied for being untimely.
The discretionary 2-month additional extension is not available to taxpayers who have an approved extension of time to file on Form 2350 (for U.S. citizens and resident aliens abroad who expect to qualify for special tax treatment).
Read more here – http://www.gemms.us/tax-extensions