72 Pa. Stat. § 9157
When the department or the register claims a decedent was domiciled in this Commonwealth at the time of his death and the taxing authority of another state makes a like claim on behalf of its state, the department may, with the approval of the Attorney General, make a written agreement of compromise with the other taxing authority and the executor or administrator of the decedent that a certain sum shall be accepted in full satisfaction of any and all inheritance taxes imposed by this Commonwealth, including any interest or penalties to the date of signing the agreement. The agreement shall also fix the amount to be accepted by the other state in full satisfaction of inheritance taxes. The executor or administrator of the decedent is authorized to make the agreement. The agreement shall conclusively fix the amount of tax payable to the Commonwealth without regard to any other provision of the laws of this Commonwealth. Unless the tax agreed upon is paid within sixty days after the signing of the agreement, interest or penalties shall accrue upon the amount fixed in the agreement, but the time between the decedent's death and the signing of the agreement shall not be included in computing the interest or penalties. In the event the aggregate amount payable under the agreement to the states involved is less than the maximum credit allowable to the estate against the Federal estate tax imposed with respect to the estate, the personal representatives shall also pay to the department so much of the difference between the aggregate amount and the amount of such credit as the amount payable to the department under the agreement bears to the aggregate amount. A copy of the agreement shall be filed in the office of the proper register, and any existing appraisement shall be deemed modified according to the agreement. In the event no appraisement has been made and filed prior to the agreement, the department shall direct an appraisement to be made and filed in the office of the proper register in accordance with the agreement.
72 P.S. § 9157