The 2021 U.S. tax calendar, courtesy of CFS Tax Solutions. JANUARY 15, 2021: 2020 4th quarter estimated taxes due. APRIL 15, 2021: 2020 individual tax returns due, individual tax return extension form due, 1st quarter 2021 estimated tax payment due, and last day to make a 2020 IRA contribution. JUNE 15, 2021: 2nd quarter 2021 estimated tax payment due. SEPTEMBER 15, 2021: 3rd quarter estimated tax payment due. OCTOBER 15, 2021: Extended individual tax returns due. See our tax planning guide for more info.