Maryland Code, Tax-General § 7-306

(a) Except as provided in § 7-307 of this subtitle, the person responsible for filing the Maryland estate tax return under § 7-305 of this subtitle shall pay the Maryland estate tax to the Comptroller no later than 9 months after the date of the death of the decedent.

(b) An extension of time to file the Maryland estate tax return granted by the Comptroller under § 7-305.1 of this subtitle does not extend the time for remitting the Maryland estate tax.

(c) If an amended Maryland estate tax return is filed pursuant to § 7-305(d) of this subtitle, the person responsible for filing the amended Maryland estate tax return shall pay the additional Maryland estate tax developed on the amended Maryland estate tax return to the Comptroller when the amended Maryland estate tax return is filed with the Comptroller.