Partnerships: File a 2017 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. 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.

S corporations: File a 2017 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 you owe in tax.

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 2018. If IRS Form 2553 is filed late, S corporation treatment will begin with calendar year 2019.

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