(c) Tax on entity's taxable income.— A tax required to be paid by a trustee on the trust's share of an entity's taxable income shall be paid proportionately:

1. (1) from income to the extent that receipts from the entity are allocated to income; and

2. (2) from principal to the extent that:

   1. (i) receipts from the entity are allocated to principal; and
   2. (ii) the trust's share of the entity's taxable income exceeds the total receipts described in paragraph (1) and subparagraph (i).