Opposition to any European patent granted by the EPO under the European Patent Convention (EPC) may be filed by any member of the public except for the proprietor himself. Opposition must be filed within nine months of the publication of the mention that the patent has been granted. The procedure may involve multiple opponents.
Opposition can only be based on the grounds specified in Article 100 EPC:
Notice of opposition must be filed online or in writing with the EPO (Munich, The Hague or Berlin), and an opposition fee is payable (see the current "Schedule of fees and expenses"). Oppositions can be filed either online using EPO software or by submitting the EPO opposition form (Form 2300), which contains all the necessary information to ensure that the opposition is admissible.
There are three possible outcomes at the end of the proceedings:
The opposition applies to all states designated in the European patent. As with any other final decision of first-instance divisions, decisions by opposition divisions can be appealed within two months from the date of notification of the decision.