September 17, 2018 @ 12:00 am - September 18, 2018 @ 12:00 am Partnerships: File calendar year Form 1065 if you timely requested a 6-month extension.
September 17, 2018 @ 12:00 am - September 18, 2018 @ 12:00 am Corporations: File calendar year Form 1120S if you timely requested a 6-month extension.