From the returns, and from any other information in the Commissioner's possession, or from any one or more of these sources, the Commissioner must make an assessment of:
(a) the amount of the taxable income (or that there is no taxable income) of any taxpayer; and
(b) the amount of the tax payable thereon (or that no tax is payable); and
(c) the total of the taxpayer's tax offset refunds (or that the taxpayer can get no such refunds).