Who is responsible for filing the Maryland estate tax return?

The duly appointed personal representative of the decedent's estate must file the return. If there is more than one personal representative, the return must be made jointly by all. If there is no personal representative appointed, every person in actual or constructive possession of any property of the decedent is required to make and file a return. See What are the requirements for filing a Maryland estate tax return? to determine if you are required to file.