(1) The Commissioner may assess a tax liability.
(2) An assessment of a tax liability is:
(a) a determination that a specified amount of tax, or that no tax, is payable by a particular person, or in respect of a particular instrument, transaction or event, under a taxation law; or
(b) a determination that a particular person, or a particular instrument, transaction or event, is liable to, or exempt from, tax under a taxation law.