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:

  • that the subject-matter of the patent is not patentable within the terms of Articles 52-57 EPC,
  • that the invention is not disclosed clearly and completely enough for a person skilled in the art to carry it out,
  • that the patent's subject-matter extends beyond the content of the application as filed.

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 is rejected and the patent is maintained as granted,
  • the patent is maintained in an amended form, in which case a new patent specification is published,
  • the patent is revoked.

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.