Before confirming that the taxpayer’s Federal Court motion for judicial review had represented an impermissible collateral attack on assessments made under ETA s. 296, Kasirer J stated (at para. 49):
Okalta Oils — like other cases that rely on a like definition of “assessment” — stands for the proposition that a tax assessment is a non-discretionary determination of the Minister as to “the actual sum in tax which the taxpayer is liable to pay” … . When assessing tax due under the ETA, the Minister is not exercising a discretionary power than can be abused. Assessing tax is, for the Minister, not a discretionary decision but a mandatory duty imposed by statute, specifically by ss. 275 and 296 of the ETA. … Rennie J.A. rightly said, at para. 17 of his reasons, that the “fulfillment of [a non-discretionary] statutory responsibility cannot be an improper motive for the Minister to issue an assessment”.