(1) Where a taxpayer establishes that, owing to his or her retirement from his or her occupation, or from any other cause (but not including a change in the investment of assets from which assessable income was derived into assets from which the taxpayer derives income which is not liable to be assessed under this Act), his or her taxable income has been permanently reduced to an amount which is less than two - thirds of his or her average taxable income, he or she shall be assessed, and the provisions of this Division shall apply to the income thereafter derived by him or her, as if he or she had never been a taxpayer before that year.
(2) For the purposes of the application of subsection (1) in relation to a taxpayer in relation to a year of income, a reference in that subsection to the average taxable income of the taxpayer shall be construed as a reference to the amount that would be the average income of the taxpayer in relation to that year of income ascertained in accordance with section 149 if there were excluded from the assessable income of the taxpayer of the average years any income received by him or her from sources from which he or she does not usually receive income.