Here are a few key tax-related deadlines for individuals through the rest of 2018. JUNE 15: Pay second installment of 2018 estimated taxes, if applicable. SEPT. 17: Pay third installment of 2018 estimated taxes, if applicable. OCT. 15: File a 2017 income tax return and pay any tax, interest and penalties due, if an automatic six-month extension was filed. DEC. 31: Incur various expenses that potentially can be deducted on your 2018 tax return. Contact us for more information about the filing requirements and to ensure you’re meeting all applicable deadlines.