139ZP.— (1) Subject to the provisions of this Part and Schedule 4, any rules made under section 139ZN and any guidelines made under section 139ZO, an authorised officer may follow such procedures for the F258[conduct of an investigation, or the exercise of powers under section 139ZK as applied by section 139ZKA] as he or she considers appropriate.

(2) An authorised officer shall, in the conduct of an investigation, take reasonable steps to keep the F258[inquiry subject] informed as to the progress of the investigation.]