לא יודע, אבל זה הרמז שמצאתי:
Full tax liability attaches to the entire amount of assets received if the deceased is a German resident at the time of his/her death, if the donor is a German resident at the time of the donation, or if the recipient is a German resident when the tax becomes chargeable. If none of the parties involved is a German resident, the transfer becomes taxable to the extent that it involves certain German domestic assets as described in section 121 of the Valuation Act.
(מתוך מסמך רשמי של רשות המסים הגרמנית).