Interpretation of s 23F(2) of the Income Tax Act 58 of 1962 (the ITA), read with the definition of ‘trading stock’ in s 1 of the ITA and the application thereof to the respondent’s business operations: such operations involving a manufacturing process: respondent excluded unquantified sales of concentrate from its gross income under s 24M of the ITA: commissioner entitled to invoke s 23F(2) of the ITA by disallowing a percentage of the s 11(a) deductions claimed by respondent.