Final answer:
Extension due dates for corporations, partnerships, and individuals typically fall on the 15th day of the fourth or third month after the end of the fiscal year, with a six-month extension moving the deadline to October 15th for calendar year taxpayers.
Step-by-step explanation:
The extension due dates for different types of taxpayers in the United States are specific to each category, such as corporations, partnerships, and individuals. Generally, corporations and partnerships are required to file their tax returns or request an extension by the 15th day of the fourth month after the end of their fiscal year. For those that follow the calendar year, this date would typically be April 15th. However, for C corporations that end their tax year on June 30th, the due date is the 15th day of the third month after the end of their fiscal year, which would be September 15th. An extension provides an additional six months to file, moving the deadline to October 15th for corporations partnerships, and businesses with fiscal years ending on December 31st. For individual taxpayers, the deadline to file a tax return or request an extension is usually April 15th, with the extension providing an additional six months, making the extended due date October 15th.