AOP and BOI taxation depends on member share certainty, with maximum marginal rate applying in key cases. Income tax rates for an AOP or BOI depend on whether members' shares are known or indeterminate and whether any member is taxed above the maximum marginal rate. Unknown or indeterminate shares attract the maximum marginal rate, while known shares may still be taxed at that rate where a member's other income exceeds the basic exemption limit. If a member is taxable at a higher rate, that member's share is taxed at the higher rate and the balance at the maximum marginal rate. In other cases, the normal individual rate applies.