26 CFR §1.662(b)-2

When a charitable contribution is made, the principles contained in §§ 1.652(b)-1 and 1.662(b)-1 generally apply. However, before the allocation of other deductions among the items of distributable net income, the charitable contributions deduction allowed under section 642(c) is (in the absence of specific allocation under the terms of the governing instrument or the requirement under local law of a different allocation) allocated among the classes of income entering into the computation of estate or trust income in accordance with the rules set forth in paragraph (b) of § 1.643(a)-5. In the application of the preceding sentence, for the purpose of allocating items of income and deductions to beneficiaries to whom income is required to be distributed currently, the amount of the charitable contributions deduction is disregarded to the extent that it exceeds the income of the trust for the taxable year reduced by amounts for the taxable year required to be distributed currently. The application of this section may be illustrated by the following examples (of which example (1) is illustrative of the preceding sentence):