A domestic bank is obliged to also include assets in the notification within the meaning of § 33 para. 1 Inheritance and Gift Tax Act (IGTA) which are in its custody or administered by a non-domestic dependent branch office even if they are covered by the local banking secrecy.
The notification within the meaning of § 33 para. 1 IGTA complies with Union law insofar as it refers to assets of a dependent branch office in a member of the European Union. The duty of notification does not impinge on the territorial sovereignty of the foreign state.
Those who deal with the custody or administration of another person’s assets by way of business (e.g. financial institutions, insurance companies), have to notify the tax office, which is competent for the administration of the inheritance tax, in written of these assets, which are in their custody, and of these claims, which are addressed to him, and which formed part of the deceased’s estate, or which were at the deceased’s disposition at the time of his death.
For more details see Koeniger, The German Inheritance and Gift Tax, 2017, p. 337 et seqq.