April 18, 2017: In 2017, April 15th is on a Saturday and the following Monday is a public holiday, Emancipation Day, so the tax deadline has been moved to the 18th. All personal, c-corporation, or estate/trust tax returns or extensions must be filed by this date. This means that all returns or extensions need to by postmarked or transmitted for e-filing by 4/18/17. Remember, additional taxes owed must be paid by this date, regardless of whether or not an extension has been filed.
June 15, 2017: Deadline for U.S. citizens or residents that work and live abroad (including military personnel) to file a personal return for 2016. This is also the due date for the 2nd installment of 2017 estimated tax payments.
September 15, 2017: Final deadline for C-corporation, S-corporation, partnership or estate/trust owners who filed an extension to file a tax return. This is also the due date for the 3rd installment of 2016 estimated tax payments.
October 16, 2017: Last call to file a 2016 personal tax return if you filed an extension on, or before, April 18, 2017.
January 16, 2018: Due date for the 4th installment of estimated tax payments for people who kept up with their estimated 2017 quarterly payments.