Calendar-Year S Corporations: Filing a 2017 income tax return (Form 1120S) or filing for an automatic six-month extension (Form 7004), and paying any tax due.

Calendar-Year Partnerships: Filing a 2017 income tax return (Form 1065 or Form 1065-B) or requesting an automatic six-month extension (Form 7004).

Individuals: Filing a 2017 income tax return (Form 1040, Form 1040A or Form 1040EZ) or filing for an automatic six-month extension (Form 4868), and paying any tax due. (See June 15 for an exception for certain taxpayers.)

Individuals: Paying the first installment of 2018 estimated taxes, if not paying income tax through withholding (Form 1040-ES).

Individuals: Making 2017 contributions to a traditional IRA or Roth IRA (even if a 2017 income tax return extension is filed).

Individuals: Making 2017 contributions to a SEP or certain other retirement plans (unless a 2017 income tax return extension is filed).

Individuals: Filing a 2017 gift tax return (Form 709) or filing for an automatic six-month extension (Form 8892), and paying any gift tax due; or filing for an automatic six-month extension (Form 4868) to extend both Form 1040 and, if no gift tax is due, Form 709.

Household Employers: Filing Schedule H (Form 1040), if wages paid equal $2,000 or more in 2017 and Form 1040 is not required to be filed. For those filing Form 1040, Schedule H is to be submitted with the return and is thus extended to the due date of the return.

Trusts and Estates: Filing an income tax return for the 2017 calendar year (Form 1041) or filing for an automatic five-and-a-half month extension to October 1 (Form 7004), and paying any income tax due.

Calendar-Year C Corporations: Filing a 2017 income tax return (Form 1120) or filing for an automatic six-month extension (Form 7004), and paying any tax due.

Calendar-Year Corporations: Paying the first installment of 2018 estimated income taxes.

Exempt Organizations: Filing a 2017 calendar-year information return (Form 990, Form 990-EZ or Form 990-PF) or filing for an automatic six-month extension (Form 8868) and paying any tax due.

Small Exempt Organizations (with gross receipts normally of $50,000 or less): Filing a 2017 e-Postcard (Form 990-N), if not filing Form 990 or Form 990-EZ.

Individuals: Filing a 2017 individual income tax return (Form 1040) or filing for a four-month extension (Form 4868), and paying any tax and interest due, if you live outside the United States.

Individuals: Paying the second installment of 2018 estimated taxes, if not paying income tax through withholding (Form 1040-ES).

Calendar-Year Corporations: Paying the second installment of 2018 estimated income taxes.

Employers: Reporting income tax withholding and FICA taxes for second quarter 2018 (Form 941), and paying any tax due.

Employers: Filing a 2017 calendar-year retirement plan report (Form 5500 or Form 5500-EZ) or requesting an extension.

Individuals: Paying the third installment of 2018 estimated taxes, if not paying income tax through withholding (Form 1040-ES).

Calendar-Year Corporations: Paying the third installment of 2018 estimated income taxes.

Calendar-Year S Corporations: Filing a 2017 income tax return (Form 1120S) and paying any tax, interest and penalties due, if an automatic six-month extension was filed.

Calendar-Year S Corporations: Making contributions for 2017 to certain employer-sponsored retirement plans, if an automatic six-month extension was filed.

Calendar-Year Partnerships: Filing a 2017 income tax return (Form 1065 or Form 1065-B), if an automatic six-month extension was filed.

Trusts and Estates: Filing an income tax return for the 2017 calendar year (Form 1041) and paying any tax, interest and penalties due, if an automatic five-and-a-half month extension was filed.

Employers: Establishing a SIMPLE or a Safe-Harbor 401(k) plan for 2018, except in certain circumstances.

October 15

Individuals: Filing a 2017 income tax return (Form 1040, Form 1040A or Form 1040EZ) and paying any tax, interest and penalties due, if an automatic six-month extension was filed (or if an automatic four-month extension was filed by a taxpayer living outside the United States).

Individuals: Making contributions for 2017 to certain existing retirement plans or establishing and contributing to a SEP for 2017, if an automatic six-month extension was filed.

Individuals: Filing a 2017 gift tax return (Form 709) and paying any tax, interest and penalties due, if an automatic six-month extension was filed.

Calendar-Year C Corporations: Filing a 2017 income tax return (Form 1120) and paying any tax, interest and penalties due, if an automatic six-month extension was filed.

Calendar-Year C Corporations: Making contributions for 2017 to certain employer-sponsored retirement plans, if an automatic six-month extension was filed.

October 31

November 15

December 17

December 31