12.—(1) Where an Appeals Officer is of the opinion that, in the particular circumstances of an appeal, it is appropriate in the interests of justice to request a party or other person who has made or was entitled to make submissions or observations to the Appeals Officer in relation to the appeal to make submissions or observations in relation to any matter which has arisen in relation to the appeal, he or she may, in his or her discretion, notwithstanding section 8(3) 10(4), 11(3) or 16(4), serve on the party or person a notice—

(a) requesting the party or person, within a period specified in the notice (being not less than 14 or more than 28 days beginning on the date of service of the notice) to submit to the Appeals Officer submissions or observations in relation to the matter, and

(b) stating that, if submissions or observations are not received before the expiration of the specified period, the Appeals Officer will, after the expiration of that period and without further notice to the party or person, pursuant to section 16(2), determine the appeal.

(2) A party or other person shall not be entitled to elaborate in writing on submissions or observations made in response to a request under subsection (1) or make further submissions or observations in writing in relation to the matter concerned, and any such elaboration, or further submissions or observations shall not be considered by an Appeals Officer.