The principle that it is the net income, i.e., net of expenditure relatable thereto, which is subject to tax and, correspondingly, not liable to tax, i.e., where it does not form part of the total income, is well established. Equally well settled is the principle that once an income is liable (or not liable) to tax, all expenditure relatable thereto is to be reckoned, and it matters little that the said expenditure has indeed resulted in a positive income, or in whatever sum. It is in fact this, i.e., the expenditure being higher than the gross income, which could be nil, that leads to the phenomenon of loss, which could therefore be across both the categories income, i.e., taxable or non-taxable, being essentially a matter of fact