6.—(1) In any case in which an appellant has not sent to the Board further particulars in accordance with a notice sent by the Board under rule 3 the tribunal may, on the application of the Board, by notice direct the appellant to supply such further particulars of the grounds on which he intends to rely and of any facts and contentions relevant thereto as may be specified in the notice, and the appellant shall send such particulars to the Secretary within such time as the tribunal shall direct.
(2) Upon receipt of further particulars from the appellant the Secretary shall send a copy thereof to the Board.
(3) If the appellant fails to comply with a direction made by the tribunal under this rule the tribunal may on the application of the Board dismiss the appeal or give such other directions as it thinks fit.
(4) A tribunal may at any time by notice direct the Board to furnish any particulars relating to the assessment to a levy which appear to be requisite for the decision of the appeal, and thereupon the Board shall send those particulars to the Secretary and to the appellant.