Commonwealth Consolidated Acts Commonwealth Consolidated Acts(1) For the purposes of the application of this Division in relation to a taxpayer in relation to a year of income, a reference in this Division to the average income of the taxpayer shall be construed as a reference to the average of the taxable incomes of the taxpayer of the years of income (in this Division referred to as average years ) beginning with the first average year and ending with the first - mentioned year of income.