Del. Code tit. 30 § 1702
Where this State and 1 or more other states each claims that it was the domicile of a decedent at the time of death and where no judicial determination of domicile for death tax purposes has been made in any of such states, any executor or the taxing official of any such state may elect to invoke this chapter. Such election shall be evidenced by the sending of a notice by registered mail, receipt requested, to the taxing officials of each such state and to each executor, ancillary administrator and interested person. Any executor may reject such election by sending a notice by registered mail, receipt requested, to the taxing officials involved and to all other executors within 40 days after the receipt of such notice of election. If such election is rejected, no further proceedings shall be had under this chapter. If such election is not rejected, the dispute as to the death taxes shall be determined solely as provided in this chapter, and any proceedings that may have been theretofore taken in this State to determine or assess such death taxes in the courts or otherwise shall be annulled and of no effect.
30 Del. C. § 1702