To comply with your obligations, Marketplace sellers have 3 main steps:
1. Announce an Authorized Representative:
It is mandatory for a marketplace seller, who is not based in Austria, to announce an Authorized Representative.
The Authorized Representative Agreement needs to be certified by a notary or by some equivalent institution if allowed in the respective country of the marketplace seller.
The Authorized Representative becomes liable with regards to the marketplace sellers Extended Producers Responsibilities and is allowed to sign a contract with a PRO in the name of the marketplace seller, see point 2.
The Austrian Authority accepts the Authorized Representative registrations quarterly.
2. Join a PRO (ERP Austria):
The marketplace seller must join a PRO in order to legally comply with its WEEE. Conclude your contract here.
There is no threshold, you have to report your put on market volumes to a PRO.