- Report income tax withholding and FICA taxes for second quarter 2018 (Form 941), and pay any tax due. (See the exception below, under “August 10.”)
- File a 2017 calendar-year retirement plan report (Form 5500 or Form 5500-EZ) or request an extension.
- Report income tax withholding and FICA taxes for second quarter 2018 (Form 941), if you deposited on time and in full all of the associated taxes due.
- If a calendar-year C corporation, pay the third installment of 2018 estimated income taxes.
- If a calendar-year S corporation or partnership that filed an automatic six-month extension:
- File a 2017 income tax return (Form 1120S, Form 1065, or Form 1065-B) and pay any tax, interest, and penalties due.
- Make contributions for 2017 to certain employer-sponsored retirement plans.