S corporations. File a 2018 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. Then, file Form 1120S and provide each partner with a copy of their final or amended (if required) Schedule K-1 by September 16.
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 2019. If Form 2553 is filed late, S corporation treatment will begin with calendar year 2020.