When do I need to file an authorisation?

As a rule, professional representatives, legal practitioners and associations do not need to file an authorisation. They are required to file a signed authorisation only where the EPO is informed of a change of representative (and the new representative is not a member of the same association or law firm, as the case may be) without the previous representative having withdrawn their appointment, or upon invitation from the EPO. An invitation is sent if the circumstances of the case require an authorisation to be filed, in particular if the EPO has doubts as to the representative's entitlement to act (OJ EPO 2024, A75, and OJ EPO 2024, A77). 

However, an employee acting on behalf of an applicant (Art. 133(3) EPC) but who is not a professional representative or legal practitioner must always file a signed authorisation.  

See What are the formal requirements for a valid authorisation?