D.C. Mun. Regs. tit. 9, r. 9-201
The taxable situs of real estate is the place where the real estate is situated.
The taxable situs of tangible personal property is the place where the property is physically located at the time of the decedent's death, except as otherwise provided in this section.
The taxable situs of tangible personal property which, by its nature, is readily movable shall be determined by the Deputy Chief Financial Officer from the facts of each case.
If readily movable property belonging to a decedent domiciled within the District is accidentally or casually outside of the District at the time of the decedent's death, the taxable situs of that property shall be the District.
The taxable situs of intangible personal property belonging to a non-alien decedent is the place where the decedent was domiciled at the time of death, except as otherwise provided by this section.
If the non-alien decedent during his or her lifetime caused intangible personal property to become an integral part of a business, trade, profession, or vocation carried on by the owner and localized in the District, that property acquires a "business situs" in the District and has a taxable situs in the District.
Whether the intangible personal property of a non-alien decedent has acquired a "business situs" in the District shall be determined by the Deputy Chief Financial Officer. In making a determination, the Deputy Chief Financial Officer may consider evidence such as affidavits, bank records, court records, agreements, and any other evidence which appears material.
Generally, all property of an alien decedent situated within the District at the time of the decedent's death has a taxable situs in the District, regardless of the domicile of the alien at the time of the alien's death.
No tax is imposed upon any transfer of securities specifically exempted under the provisions of § 15 of Article 3 of the Act, even though the securities were issued by or are obligations of a corporation organized under the laws of the District.
D.C. Mun. Regs. tit. 9, r. 9-201