12(1)At any time when an enquiry is in progress into a self-certificate any question arising in connection with the subject-matter of the enquiry may be referred to the Special Commissioners for their determination.
(2)Notice of referral must be given—
(a)jointly by the purchaser and the Inland Revenue,
(b)in writing,
(c)to the Special Commissioners.
(3)The notice of referral must specify the question or questions being referred.
(4)More than one notice of referral may be given under this paragraph in relation to an enquiry.
(5)For the purposes of this paragraph the period during which an enquiry is in progress is the whole of the period—
(a)beginning with the day on which the notice of enquiry was given, and
(b)ending with the day on which the enquiry is completed.