March 16, 2015
Corporations: File Form 1120 for calendar year and pay any tax due. For automatic 6-month extension, file Form 7004 and deposit estimated tax.
S-Corporations: File Form 1120S for calendar year and pay any tax due. Furnish a copy of Schedule K-1 to each shareholder. File Form 2553 to elect S Corporation status beginning with calendar year 2015.