Due Dates Returns for individuals. fiduciaries and partnerships are due on or before fifteenth day of fourth month following year-end of entity EXtensions for filing deadline available, but tax must be paid by original due date to avoid penalties 1010 Due Dates Returns for individuals, fiduciaries and partnerships are due on or before fifteenth day of fourth month following year-end of entity Extensions for filing deadline available, but tax must be paid by original due date to avoid penalties