Partnerships: File a 2018 calendar-year return (IRS Form 1065). Provide each partner with a copy of Schedule K-1 (IRS Form 1065), Partner’s Share of Income, Deductions, Credits, etc., or a substitute Schedule K-1 (IRS Form 1065). If you want an automatic six-month extension of time to file the return and provide Schedule K-1 or a substitute Schedule K-1, file IRS Form 7004. Then, file IRS Form 1065 and provide each partner with a copy of his or her final or amended (if required) Schedule K-1 by September 16.

S corporations: File a 2018 calendar-year income tax return (IRS Form 1120S) and pay any tax due. Provide each shareholder with a copy of Schedule K-1 (IRS 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 IRS Form 7004 and deposit what you estimate that you owe. Then, file the return, pay any tax, interest, and penalties due, and provide each shareholder with a copy of the Schedule K-1 (IRS Form 1120S) by September 16.

S corporation election: File IRS Form 2553, Election by a Small Business Corporation, to choose to be treated as an S corporation beginning with calendar year 2019. If IRS Form 2553 is filed late, S corporation treatment will begin with calendar year 2020.

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