In computing the deduction allowable under to a trust, no amount otherwise allowable under as a deduction shall be allowed as a deduction with respect to income of the taxable year which is allocable to its unrelated business income for such year. For purposes of the preceding sentence, the term “unrelated business income” means an amount equal to the amount which, if such trust were exempt from tax under by reason of , would be computed as its unrelated business taxable income under section 512 (relating to income derived from certain business activities and from certain property acquired with borrowed funds).
For disallowance of certain charitable, etc., deductions otherwise allowable under , see sections 508(d) and 4948(c)(4).