Currently the extension due dates for calendar year Partnerships and Estates fall on October 15th, which is the same day that Individual tax return extensions are due. Often times this causes problems for those individuals who are waiting for a K-1 to complete their 1040. The IRS has recognized this problem and starting with businesses who have a tax year ending September 30, 2008 and later, the 1065 Partnership returns and the 1041 Estate returns will only be granted extensions of 5 months instead of six.
For calendar year tax payers, this means that instead of the extended due date being October 15th, it will be September 15th. This change does not affect S-Corporations as they currently have a due date of March 15th, which with a 6 month extension still has them due by September 15th.