Any question about the way in which a sum is to be apportioned under section 929 must be determined in accordance with section 563(2) to (6) of CAA 2001 (procedure for determining certain questions affecting two or more persons) if it materially affects two or more taxpayers.

For the purposes of subsection (1) a question materially affects two or more taxpayers if at the time when the question falls to be determined it appears that the determination is material to the liability to tax (for whatever period) of two or more persons.