The binding legal principles established are: (1) A court will interfere with a taxing officer's discretion only where the officer acted on a wrong principle, failed to exercise discretion, was grossly unreasonable, or was clearly wrong on an item. (2) In relation to counsel fees claimed as disbursements, the taxing officer must enquire into necessity and reasonableness as required by Rule 72(3) and Rule 72(8)(a); allowing fees without bringing the mind to bear on the propriety of recovery is reviewable. (3) Where the taxation discretion has arguably not been properly exercised and the record does not allow the court to fix quantum without itself descending into taxation, a de novo taxation is the appropriate remedy rather than substitution. (4) Where a taxing officer's account of the taxation proceedings is itself a central disputed question in the review, the interests of justice and integrity of the taxation process require that fresh taxation should not take place before the same officer, and the matter should be allocated to a different taxing officer. (5) Compliance with Rule 72(28) should be assessed substantively rather than purely formalistically; where the dispute is concrete and identifiable and the respondents have engaged on the merits, the review threshold is met.