26 U.S. Code § 2624 - Valuation
Except as otherwise provided in this chapter, property shall be valued as of the time of the generation-skipping transfer.
In the case of any direct skip of property which is included in the transferor’s gross estate, the value of such property for purposes of this chapter shall be the same as its value for purposes of chapter 11 (determined with regard to sections 2032 and 2032A).
If 1 or more taxable terminations with respect to the same trust occur at the same time as and as a result of the death of an individual, an election may be made to value all of the property included in such terminations in accordance with section 2032.
For purposes of this chapter, the value of the property transferred shall be reduced by the amount of any consideration provided by the transferee.