Taxation of association income when member shares unknown: income taxed at maximum marginal rate unless member's rate is higher. If members' shares in an association of persons or body of individuals are indeterminate or unknown, the association's total income is taxed at the maximum marginal rate, except that if any member's personal tax rate exceeds that rate, the higher rate applies. If shares are known but certain members have taxable incomes or rates above the maximum marginal rate, income portions attributable to them are taxed at those higher rates while the balance is taxed at the maximum marginal rate.