26 U.S.C. § 2518

1. (a)For purposes of this subtitle, if a person makes a qualified disclaimer with respect to any interest in property, this subtitle shall apply with respect to such interest as if the interest had never been transferred to such person.
2. (b)For purposes of subsection (a), the term “qualified disclaimer” means an irrevocable and unqualified refusal by a person to accept an interest in property but only if—
   1. (1)such refusal is in writing,
   2. (2)such writing is received by the transferor of the interest, his legal representative, or the holder of the legal title to the property to which the interest relates not later than the date which is 9 months after the later of—
      1. (A)the day on which the transfer creating the interest in such person is made, or
      2. (B)the day on which such person attains age 21,
   3. (3)such person has not accepted the interest or any of its benefits, and
   4. (4)as a result of such refusal, the interest passes without any direction on the part of the person making the disclaimer and passes either—
      1. (A)to the spouse of the decedent, or
      2. (B)to a person other than the person making the disclaimer.
3. (c)For purposes of subsection (a)—
   1. (1)A disclaimer with respect to an undivided portion of an interest which meets the requirements of the preceding sentence shall be treated as a qualified disclaimer of such portion of the interest.
   2. (2)A power with respect to property shall be treated as an interest in such property.
   3. (3)A written transfer of the transferor’s entire interest in the property—shall be treated as a qualified disclaimer.
      1. (A)which meets requirements similar to the requirements of paragraphs (2) and (3) of subsection (b), and
      2. (B)which is to a person or persons who would have received the property had the transferor made a qualified disclaimer (within the meaning of subsection (b)),