Individuals

If you are not paying your 2017 income tax through withholding (or you will not pay enough tax during the year that way), pay the third installment of your 2017 estimated tax. Use Form 1040-ES (Estimated Tax for Individuals). For more information, see IRS Publication 505 (Tax Withholding and Estimated Tax).

Partnerships

If a 6-month tax extension was requested/obtained, file a 2016 tax return (Form 1065) and pay any tax due by this date. Provide each shareholder with a copy of their final or amended Schedule K-1 (Form 1065) or substitute Schedule K-1 (Form 1065).

S Corporations

If a 6-month tax extension was requested/obtained, file a 2016 tax return (Form 1120S) and pay any tax due by this date. Provide each shareholder with a copy of their final or amended Schedule K-1 (Form 1120S) or substitute Schedule K-1 (Form 1120S).

Corporations

Deposit the third installment payment for 2017 estimated income tax. Form 1120-W (Estimated Tax for Corporations) is a worksheet that can be used to estimate your tax for the year.