The opposition procedure before the European Patent Office (EPO) is a post-grant , contentious, inter partes, administrative procedure intended to allow any European patent to be centrally opposed if it was allegedly wrongly granted. Basically European patents granted by the EPO under the European Patent Convention (EPC) may be opposed by any person from the public. This happens often when some prior art was not found during the grant procedure, but was only known by third parties.

The opposition can only be based on grounds mentioned in Art. 100 of the Convention [1], i.e. on the grounds that the patent is not patentable, on the grounds that it is not sufficiently described to allow a person skilled in the art to carry out the invention, or on the grounds that the content of the patent extends beyond the content of the application as filed.

The notice of opposition must be filed in writing at the EPO (either at Munich, The Hague or Berlin) within nine months from the publication of the mention of the grant of the European patent, along with the payment of an opposition fee. Opposition divisions of the EPO are then responsible for the opposition procedure.

Issue and effects of the opposition

After opposition, the patent can be either maintained as granted, maintained in an amended form or revoked. The opposition has an effect on all designated states in the European patent.

Transfer of status opponent

This section is a stub. You can help Wikipedia by European Patent Convention, Part V, Opposition Procedure (Art. 99 to 105)