Corporations: File a 2015 calendar year income tax return (Form 1120) and pay any tax due. If you want an automatic six-month extension of time to file the return, file Form 7004 and deposit what you estimate you owe.

S Corporations: File a 2015 calendar year income tax return (Form 1120S) and pay any tax due. Provide each shareholder with a copy of Schedule K-1 (Form 1120S), Shareholder’s Share of Income, Deductions, Credits, etc., or a substitute Schedule K-1. If you want an automatic six-month extension of time to file the return, file Form 7004 and deposit what you estimate you owe.

S Corporation Election: File Form 2553, Election by a Small Business Corporation, to choose to be treated as an S corporation beginning with calendar year 2016. If Form 2553 is filed late, S corporation treatment will begin with calendar year 2017.

Electing Large Partnerships: Provide each partner with a copy of Schedule K-1 (Form 1065-B), Partner’s Share of Income (Loss) From an Electing Large Partnership, or a substitute Schedule K-1. This due date applies even if the partnership requests an extension of time to file the Form 1065-B by filing Form 7004.

Employers: For Social Security, Medicare, withheld income tax, and nonpayroll withholding, deposit the tax for payments in February if the monthly rule applies.