Treasury Regulations, Subchapter A, Sec. 1.643(c)-1
From TaxAlmanac
Sec. 1.643(c)-1 Definition of 'beneficiary'
An heir, legatee, or devisee (including an estate or trust) is a beneficiary. A trust created under a decedent's will is a beneficiary of the decedent's estate. The following persons are treated as beneficiaries:
(a) Any person with respect to an amount used to discharge or satisfy that person's legal obligation as that term is used in §1.662(a)–4.
(b) The grantor of a trust with respect to an amount applied or distributed for the support of a dependent under the circumstances specified in section 677(b) out of corpus or out of other than income for the taxable year of the trust.
(c) The trustee or cotrustee of a trust with respect to an amount applied or distributed for the support of a dependent under the circumstances specified in section 678(c) out of corpus or out of other than income for the taxable year of the trust.
