Once my tax extension is approved by the IRS, when is my extended tax return due?

S-corporations, Multi Member LLCs and Partnerships are given an extended tax return filing deadline of 6 months (September 15 if they are operating based on the calendar year, versus the fiscal year). C Corporations are also given an extended tax deadline of 6 months from their original return due date (October 15 if they are operating based on the calendar year, versus the fiscal year).