Excise Tax Due Dates IF the taxes are due under section . . .THEN file Form 5330 by the . . .497115th day of the 10th month after the last day of the plan year.4971(f)15th day of the 10th month after the last day of the plan year.4971(g)(2)15th day of the 10th month after the last day of the plan year.14 more rows