While proceedings on a referral under section 28ZA of this Act are in progress in relation to an enquiry—
(a) no partial closure notice relating to the question referred shall be given,
(aa) no final closure notice shall be given in relation to the enquiry, and
(b) no application may be made for a direction to give a notice referred to in paragraph (a) or (aa).
For the purposes of this section proceedings on a referral are in progress where—
(a) notice of referral has been given,
(b) the notice has not been withdrawn, and
(c) the questions referred have not been finally determined.
For the purposes of subsection (2)(c) above a question referred is finally determined when—
(a) it has been determined by the tribunal, and
(b) there is no further possibility of that determination being varied or set aside (disregarding any power to give permission to appeal out of time).