Securities transaction tax deduction applies only to business trading income, not to capital gains or passive investment. Deduction is available for securities transaction tax and commodities transaction tax only where the transactions are entered into in the course of business or profession and the related income is assessable under the head Profits and gains of business or profession. The allowance is confined to transaction-based taxes paid on taxable securities or commodities transactions arising from business activity, such as share trading or commodity trading, and is not available where the person is merely an investor and the income is chargeable as capital gains.