The Federal Government provides two invoice receipt platforms for the transmission of e-invoices to federal public-sector customers:
ZRE for electronic invoices to direct Federal Administration institutions (e.g. ministries and higher federal authorities).
OZG-RE for electronic invoices to entities of the indirect Federal Administration (e.g. independent entities that have taken over federal tasks).
The invoice recipients will let you know via which invoice receipt platform they can be reached.
In order to use an invoice receipt platform, you must register there (create a user account) and have the desired transmission channels activated.