Most patent disputes are fought on two fronts: infringement and validity. We attack competitors’ patents and defend our clients’ patents before the German Patent and Trade Mark Office (DPMA), the European Patent Office, the Federal Patent Court and the Unified Patent Court.
Overview
| Objective | Proceeding | Time limit | Forum |
|---|---|---|---|
| Revoke a patent cost-effectively | Opposition | 9 months from publication of grant | DPMA / EPO |
| Challenge a decision | Appeal | 1 month (DPMA) / 2 + 4 months (EPO) | Federal Patent Court / EPO Boards of Appeal |
| Revoke a German patent or the German part of a European patent later | Nullity action | After the opposition period (German patents: only once no opposition is pending) | Federal Patent Court, appeal to the Federal Court of Justice |
| Revoke a European patent for all UPC states | Revocation action or counterclaim | Any time (no opt-out) | Unified Patent Court |
| Cancel a German utility model | Cancellation request | Any time | DPMA, appeal to the Federal Patent Court |
Opposition
An opposition is the least expensive way to remove a patent. A European opposition can revoke the patent for all designated states and the Unitary Patent at once. A straw man may file, so the real party in interest need not be disclosed. An alleged infringer may intervene in pending opposition proceedings within three months of being sued.
Nullity actions in Germany
Germany applies a bifurcated system: infringement is decided by the regional courts, validity by the Federal Patent Court. The Federal Patent Court issues a preliminary opinion, usually within six months of service of the action, which often influences whether the infringement court stays its proceedings. A decision at first instance typically takes one to two years.
Recent case law
In G 1/24 (June 2025), the EPO Enlarged Board held that the description and drawings must always be consulted when interpreting claims. In G 1/25 (September 2026), it ruled that adaptation of the description can only be required where a genuine inconsistency violates a substantive EPC requirement. A further referral on claim interpretation and added matter is pending as G 1/26.
How an EPO opposition proceeds
An opposition must be filed in writing within nine months of the mention of grant in the European Patent Bulletin, with the opposition fee and a reasoned statement of the facts, evidence and arguments (Art. 99 EPC, Rule 76 EPC). The only admissible grounds are those listed in Art. 100 EPC: lack of patentability, in particular novelty and inventive step, insufficient disclosure and added matter. Lack of clarity is not a ground of opposition. Amended claims are examined for clarity only to the extent that the amendment itself introduces the problem.
The opposition division then invites the proprietor to reply and, where appropriate, to file amendments. Proprietors usually defend the patent with a main request and a series of auxiliary requests. Amendments may not extend the protection conferred (Art. 123(3) EPC), so a granted claim cannot be broadened in opposition. Most cases end after oral proceedings with one of three outcomes: revocation, rejection of the opposition, or maintenance in amended form. Each party normally bears its own costs (Art. 104(1) EPC).
For opponents, the notice of opposition is the decisive document. Facts and evidence filed late may be disregarded, and the scope of the opposition is fixed by the notice. Prior art from the opponent’s own sphere, such as earlier sales or demonstrations, needs complete documentation: invoices, drawings, witness statements and evidence of the date. The Boards of Appeal apply a strict standard of proof where only the opponent has access to the evidence.
Opposition, nullity action or UPC revocation: choosing the route
The choice depends on timing, territory and the dispute with the patentee.
- Within the opposition period, the EPO opposition is usually the first choice for European patents. It is inexpensive, covers all states and the Unitary Patent, and carries no risk of a costs order.
- After the opposition period, a German patent or the German part of a European patent can only be attacked with a nullity action at the Federal Patent Court. The action is admissible only once no opposition can be filed and no opposition is pending (§ 81(2) PatG). The losing party bears the costs, including attorney fees.
- Before the Unified Patent Court, a revocation action or counterclaim can remove a European patent that has not been opted out for all UPC states in one decision. Proceedings are fast and front-loaded, so the attack must be fully prepared when filed. See our page on the Unified Patent Court for the procedure.
These routes can run in parallel. Opponents often file an EPO opposition and, once sued, a counterclaim at the UPC or a nullity action in Germany. The patentee in turn can ask the EPO to limit its patent centrally (Art. 105a EPC), which is often used to prepare an infringement action.
If you are defending an infringement action, the validity attack belongs in the same strategy. Read more on patent infringement in Germany and on the scope of protection.
Frequently asked questions
How much does a patent opposition at the EPO cost?
The official opposition fee at the EPO is EUR 880. The main cost is the preparation of the notice of opposition, prior art searches and, where needed, oral proceedings. Each party usually bears its own costs, so the opponent does not risk paying the patentee’s attorney fees. The current official fees are listed on our page on official fees.
Can I file an opposition against a European patent anonymously?
The opponent must be named, but the opposition can be filed by a straw man, such as a professional representative acting in their own name. The EPO Enlarged Board has confirmed that this is admissible. Companies use it to avoid signalling interest in a technology to a competitor.
What can I do if the nine-month opposition period has expired?
The period cannot be extended. A German patent or the German part of a European patent can then be challenged with a nullity action at the Federal Patent Court. For European patents that are not opted out, a revocation action at the Unified Patent Court is available at any time.
Does a nullity action stop a patent infringement case in Germany?
Not automatically. The infringement court decides whether to stay its proceedings and usually does so only if it considers revocation highly likely. The preliminary opinion of the Federal Patent Court often influences that decision, so a well-founded nullity action should be filed early.
Can the patent proprietor amend the claims during opposition proceedings?
Yes. The proprietor can restrict the claims, usually by filing auxiliary requests, but cannot broaden them beyond the granted protection. Amendments must also have a basis in the application as filed.
Discuss an opposition or nullity action
Tell us briefly what you need. You will receive an initial assessment of the approach, deadlines and costs. Phone +49 511 357356-0 or use our enquiry form.