EPO opposition proceedings at the European Patent Office

Patenthuis specializes in EPO oppositions, in other words: European patent opposition procedures. We represent patent proprietors as well as opponents.

Anybody who believes a European patent was granted incorrectly, may filed opposition for a period of nine months following the grant.

The patentability of the claims is then re-evaluated, considering arguments submitted by the opponent or opponents.

An opposition is a legal procedure having strict procedural requirements, often requiring a European patent to handle opposition proceedings.

If somebody opposes your patent and you need to defend yourself, or if you wish to file an opposition against a patent that you would like to be revoked, Patenthuis can conduct the procedure for you. Whether you want to oppose a European patent or whether you need to defend your European patent against an attack by somebody else, Patenthuis is at your service.

Advantages of centralised EPO opposition proceedings.


If you want to have a European patent revoked, you have two choices: A centralised EPO opposition or national patent revocation. This last option requires legal proceedings at the national courts of the various countries in Europe.

However, there are advantages to an EPO opposition. These are mainly: reduced cost and complexity. This is the case because there is only a single, centralised procedure. Instead, if you want a European patent revoked after the nine-month opposition period, you will need to start revocation procedures country by country. This leads to complicated, long and expensive legal procedures.

There is a further advantage to EPO oppositions, at least for the opponent. If opposition is unsuccessful, you still have the possibility to try to obtain patent revocation later in the various national courts. This allows, for instance, to search harder for stronger for more prior art. This prior art can then be used in the subsequent national procedures.

Opponents and representation

An opposition against a granted European patent can be filed by anyone. No interest needs to be demonstrated.

Parties not having a residence in the EPC member states need to be represented by a European Patent Attorney. There is no such requirement for parties having a residence in one of those member states. However, it is very strongly recommended also for those parties to be represented.

An opposition is an inter partes procedure. This means in essence that the patent proprietor and the opponent(s) are parties to the proceedings, and an Oppostion Division (OD) of the EPO acts as impartial arbiter. Whereas during examination the examiners may be forthcoming to the applicant and make suggestion to expediate grant, the people in the OD need to be strictly impartial.

Timing of opposition

Opposition is a procedure provided by the European Patent Convention (EPC). It allows to centrally revoke a granted patent in Europe. The procedure needs to be started within nine months from the date of grant of a European patent. This is a very strict, non-extendible deadline.

All the arguments need to be submitted as well within this deadline. Considering that there may be significant preparatory work, you are advised to contact Patenthuis soon as possible, preferably at least 2-3 months before the nine-month deadline.

EPO opposition proceedings take place at the EPO offices in The Hague (Netherlands) or Munich (Germany)

An opposition procedure usually involves two rounds of written arguments and usually ends with oral proceedings. Immediately at the end of the oral proceedings a decision is taken.

The result of an opposition can be that the patent is revoked or upheld. A partial revocation is also possible, and is actually quite common.

Opposition Appeal

The losing party may appeal the outcome of the opposition. This needs to be done within 2 months. Patenthuis will also be happy to represent you during the appeal proceedings.

Grounds of opposition

An opposition may in practice be based on one or more of the following grounds:

The invention is not novel or inventive

This ground is the most commonly used ground. If an invention is the same as, or obviously follows from, a product or method that was available publicly before the filing date of the patent, this ground can often be invoked successfully.

Novelty and inventiveness are thoroughly investigated during pre-grant examination, but of course there may be publications that the examiner did not find or did not use. Such publications can be used during the oppostion procedure to argue that the claimed invention did not meet the basis requirements for patentability.

Often the opponent, being active in the same technical field, has better knowledge of what was made public and has access to different documents than the examiner. Typically this concerns brochures, trade magazines, symposium proceedings, exhibitions and standardisation committees. The examiners at EPO rarely use those kinds of disclosures spontaneously, because they are not so easy to find.

If the opponent does not have evidence of such public disclosures, a specific prior art search is strongly advised. Patenthuis can perform this for you.

The invention is not sufficiently disclosed

If a skilled person in the particular technical field can’t reproduce the invention without undue burden, based on his knowledge and the disclosure in the patent, the patent can be revoked in opposition. During pre-grant examination this aspect is usually not investigated in depth by the examiners, and the benefit of the doubt is often given to the applicant. This ground of opposition, if presented well, offers good prospects of success to an opponent in some cases.

Extension of subject matter

If the features as claimed were not disclosed in the application as filed, the application may not be granted. This is not uncommon, especially if the claims as granted are amended compared to the application as filed. This argument is regularly usuable.

It is especially attractive because if it is successful, it is very difficult, and in many cases impossible, for the patent proprietor to rescue part of his patent by making amendments.

Often, if it can be shown that an error, even a small error, occured in allowing an amendment during pre-grant examination, such an error is fatal to the maintenance of the patent.

Exclusion from patentability

This means that by its nature the invention should not be patentable: Eg: Not industrially applicable, not technical, medical treatments, scientific theories. This ground is not used very often in opposition.