Ind. Code § 6-4.1-5-16

Sec. 16. The department of state revenue shall, by mail, give notice of the inheritance tax due as a result of a nonresident decedent's death to the personal representative of the decedent's estate or the trustee of property transferred by the decedent. However, if there is no personal representative or trustee, the department shall give the notice to each person liable for payment of the tax. Unless an appeal is initiated under IC 6-4.1-7-5 within ninety (90) days after the notice is given, the inheritance tax stated by the department in the notice is final.