August 10
Employers. For Social Security, Medicare, and withheld income tax, file Form 941 for the second quarter of 2017. This due date applies only if you deposited the tax for the quarter in full and on time.
August 15
Employers. For Social Security, Medicare, withheld income tax, and nonpayroll withholding, deposit the tax for payments in July if the monthly rule applies.
September 15
Individuals. If you are not paying your 2017 income tax through withholding (or will not pay enough tax during the year), 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 his or her 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.