September 15
Individuals. If you are not paying your 2017 income tax through withholding (or will not pay in enough tax during the year that way), pay the third installment of your 2017 estimated tax. Use Form 1040-ES.
Employers. For Social Security, Medicare, withheld income tax, and nonpayroll withholding, deposit the tax for payments in August if the monthly rule applies.
Corporations. Deposit the third installment of estimated income tax for 2017. Use the worksheet Form 1120-W to help estimate tax for the year.
Partnerships. File a 2016 calendar-year return (Form 1065). This due date applies only if you timely requested an automatic six-month extension. Provide each partner with a copy of their final or amended Schedule K1 (Form 1065) or substitute Schedule K1 (Form 1065).
S corporations. File a 2016 calendar-year income tax return (Form 1120S) and pay any tax due. This due date applies only if you timely requested an automatic six-month extension. Provide each shareholder with a copy of Schedule K-1 (Form 1120S) or a substitute Schedule K-1.
October 2
Estates and Trusts. If you have an automatic 5 ½ month extension to file your estate (other than a bankruptcy estate which have a 6 month extension) or trust tax return for 2016, file Form 1041 and pay any tax, interest, or penalties due. This due date only applies if you timely requested an automatic 5 ½ month extension.
October 16
Individuals. If you have an automatic six-month extension to file your income tax return for 2016, file Form 1040, 1040A, or 1040EZ and pay any tax, interest, or penalties due.
Corporations. File a 2016 calendar-year income tax return (Form 1120) and pay any tax, interest, and penalties due. This due date applies only if you timely requested an automatic six-month extension.
Employers. For Social Security, Medicare, withheld income tax, and nonpayroll withholding, deposit the tax for payments in September if the monthly rule applies.
October 31
Employers. For Social Security, Medicare, and withheld income tax, file Form 941 for the third quarter of 2017. Deposit any undeposited tax. (If your tax liability is less than $2,500, you can pay it in full with a timely filed return.) If you deposited the tax for the quarter in full and on time, you have until November 13 to file the return.
For federal unemployment tax, deposit the tax owed through September if more than $500.