26 U.S.C. § 2603: Liability for tax

(a) Personal liability(1) Taxable distributionsIn the case of a taxable distribution, the tax imposed by section 2601 shall be paid by the transferee. (2) Taxable terminationIn the case of a taxable termination or a direct skip from a trust, the tax shall be paid by the trustee. (3) Direct skipIn the case of a direct skip (other than a direct skip from a trust), the tax shall be paid by the transferor. (b) Source of taxUnless otherwise directed pursuant to the governing instrument by specific reference to the tax imposed by this chapter, the tax imposed by this chapter on a generation-skipping transfer shall be charged to the property constituting such transfer. (c) Cross referenceFor provisions making estate and gift tax provisions with respect to transferee liability, liens, and related matters applicable to the tax imposed by section 2601, see section 2661.