2018 Q4 tax calendar: Key deadlines for businesses and other employers

Here are some of the key tax-related deadlines affecting businesses and other employers during the fourth quarter of 2018. Keep in mind that this list isn’t all-inclusive, so there may be additional deadlines that apply to you. Contact us to ensure you’re meeting all applicable deadlines and to learn more about the filing requirements.

October 15

If a calendar-year C corporation that filed an automatic six-month extension:
- File a 2017 income tax return (Form 1120) and pay any tax, interest and penalties due.
- Make contributions for 2017 to certain employer-sponsored retirement plans.

October 31

Report income tax withholding and FICA taxes for third quarter 2018 (Form 941) and pay any tax due. (See exception below under “November 13.”)

November 13

Report income tax withholding and FICA taxes for third quarter 2018 (Form 941), if you deposited on time and in full all of the associated taxes due.

December 17

If a calendar-year C corporation, pay the fourth installment of 2018 estimated income taxes.