26 U.S.C. § 6408: State escheat laws not to apply

No overpayment of any tax imposed by this title shall be refunded (and no interest with respect to any such overpayment shall be paid) if the amount of such refund (or interest) would escheat to a State or would otherwise become the property of a State under any law relating to the disposition of unclaimed or abandoned property. No refund (or payment of interest) shall be made to the estate of any decedent unless it is affirmatively shown that such amount will not escheat to a State or otherwise become the property of a State under such a law.