June 15
Individuals. If you are not paying your 2017 income tax through withholding (or will not pay enough tax during the year that way), pay the second installment of your 2017 estimated tax.
If you are a U.S. citizen or resident alien living and working (or on military duty) outside the United States and Puerto Rico, file Form 1040 and pay any tax, interest, and penalties due for 2016. If you want additional time to file your return, file Form 4868 to obtain four additional months to file. Then, file Form 1040 by October 16.
Corporations. Deposit the second installment of estimated tax for 2017.
Employers. For Social Security, Medicare, withheld income tax, and nonpayroll withholding, deposit the tax for payments in May if the monthly rule applies.
July 17
Employers. For Social Security, Medicare, withheld income tax, and nonpayroll withholding, deposit the tax for payments in June if the monthly rule applies.
July 31
Employers. For Social Security, Medicare, and withheld income tax, file Form 941 for the second 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 August 10 to file the return.
For federal unemployment tax, deposit the tax owed through June if more than $500.
If you maintain an employee benefit plan with a calendar year-end, file Form 5500 or 5500-EZ for calendar year 2016.