Export profit deduction under section 80HHC requires export proceeds received in convertible foreign exchange within the prescribed period for eligibility. Deduction under section 80HHC is computed by applying the ratio Export turnover/Total turnover to business profits under 'Profits and gains of business or profession.' Export turnover is the FOB sale proceeds actually received in convertible foreign exchange and must be brought into India within six months of the previous year (subject to discretionary extension). CCS, DDK and profit on sale of I/L are included in business profits but excluded from total turnover. Supporting manufacturers and processors are eligible if a disclaimer certificate in Form No.10CCAB is obtained.