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.



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