In Vienna, where Art 50 EUVAufenthaltstitel "Artikel 50 EUV" The Aufenthaltstitel "Art 50 EUV" is a residency title to be issued to British citizens from the end of the transition period. Its name is derived from Article 50 of the Treaty on European Union. The "Titel" refers to the document or card itself, and not the right, or permission that it confirms. cards are sent out by post, using an RsA-Brief, recipients are required to sign for their card personally. If you are not in when the postman delivers, you receive a yellow slip and have to sign (taking a photo ID (e.g. your passport) with you to the post office listed on the yellow slip.
If you are away for an extended period and expecting delivery of your card, to avoid that your card is returned to MA35Magistratsabteilung 35 Residency and citizenship issues in Vienna are handled by Magistratsabteilung 35 (MA35). It has several offices in Vienna and where you need to go depends on whether or not you are an EU citizen (you go to one or other of its EU Referat offices depending on the district you live in), or its premises for third country nationals. as undelivered, you can set up a Vertretungsvollmacht. This allows you to nominate any person legally resident at an Austrian address to represent you.
The process is simple, you would need to send the completed form, along with a copy of an ID of the person you are nominating, to MA35 and then your card would be delivered the nominated person’s address.
Further information about powers of attorney and/or representation (Vollmacht/Vertretung) can be found here.
H/T: Friedrich Bruckner, Wirtschaftsagentur, Expat Center