‘tax position’ means an assumption underlying one or more aspects of a tax return, including whether or not-

(a)     an amount, transaction, event or item is taxable;

(b)     an amount or item is deductible or may be set-off;

(c)     a lower rate of tax than the maximum applicable to that class of taxpayer, transaction, event or item applies; or

(d)     an amount qualifies as a reduction of tax payable; and