At any time when an enquiry is in progress under section 9A(1) or 12AC(1) of this Act in relation to any matter, any question arising in connection with the subject-matter of the enquiry may be referred to the tribunal for its determination.
Notice of referral must be given—
jointly by the taxpayer and an officer of the Board,
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
to the tribunal.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
More than one notice of referral may be given under this section in relation to an enquiry.
For the purposes of this section the period during which an enquiry is in progress in relation to any matter is the whole of the period—
beginning with the day on which notice of enquiry is given, and
ending with the day on which a partial closure notice is issued in relation to the matter or, if no such notice is issued, a final closure notice is issued.
In this section "the taxpayer" means—
in relation to an enquiry under section 9A(1) of this Act, the person to whom the notice of enquiry was given;
in relation to an enquiry under section 12AC(1) of this Act, the person to whom the notice of enquiry was given or his successor.