Separate computation of commercial activity gains for registered non-profit organisations requires distinct accounting and tax treatment. Gains from commercial activities permitted to a registered non-profit organisation are computed separately for the relevant tax year by treating the activity as distinct from the organisation, maintaining separate books of account, and applying the computation provisions of Part D of Chapter IV of the Act. The rule establishes a segregation-based method for tax computation and requires the commercial activity to be accounted for independently from the non-profit organisation's other operations.