https://www.epo.org/en/service-support/faq/law-practice/list-professional-representatives-entry/what-point-does-one-become
At what point does one become a European patent attorney or "professional representative before the European Patent Office"?
According to Article 134(1), (5) EPC, entry on the list of professional representatives before the EPO has a constitutive effect. After registration, the designations “zugelassener Vertreter vor dem EPA", "European patent attorney" and "mandataire en brevets européens" may be used.