1. The Missouri taxable income of a nonresident estate or trust consists of:

(1) Its share under section 143.391 of items of income, gain, loss, and deduction from sources within Missouri which enter into the federal definition of distributable net income;

(2) Increased or reduced by the amount of any items of income, gain, loss, or deduction from sources within Missouri which are recognized for federal income tax purposes but excluded from the federal definition of distributable net income of the estate or trust;

(3) To the extent relating to items within subdivision (2) of this subsection 1, there shall be added or subtracted, as the case may be, the modifications described in sections 143.121 and 143.141, and there shall be subtracted the federal income tax deduction provided in section 143.171. These additions and subtractions shall only apply to the extent that they are not determinants of the federal distributable net income of the estate or trust.

(4) There shall be subtracted a fractional share of the federal personal exemption deduction to which such nonresident estate or trust is entitled the numerator of which shall be the federal distributable net income derived from Missouri sources and the denominator of which shall be the federal distributable net income.

2. The sources of items of income, gain, loss, or deduction shall be determined under regulations prescribed by the director of revenue in accordance with the general rules in section 143.181 as if the estate or trust were a nonresident individual.