EPO Opposition Proceedings: 6 Proven Steps to Win

A competitor just had a European patent granted, and it blocks your product across the entire EU. You have two options: fight it country by country in national courts, slowly and expensively, or kill it everywhere at once with a single action. EPO opposition proceedings are that single action, the cheapest and most powerful way to challenge a granted European patent centrally. But there is a catch that ends most cases before they start: you have nine months, and not a day more. This guide walks through the deadline, the grounds that actually work, the procedure, and how to build a case that wins.

What EPO Opposition Proceedings Actually Do

Once the European Patent Office grants a patent, that patent splits into a bundle of national rights across the states the applicant designated. EPO opposition proceedings let any third party attack the whole bundle in one centralized procedure at the EPO itself, rather than suing in each national court. If the opposition succeeds, the patent is revoked or narrowed in every designated state simultaneously.

That central effect is the entire appeal. A national revocation action bites in one country only; an opposition handled by the EPO, governed by Article 99 of the European Patent Convention, reaches them all. It is slower than an injunction but dramatically cheaper than parallel litigation across Europe, which is why it is the default first move when a rival’s patent is in your way.

The 9-Month Clock: When It Starts

The opposition window is exactly nine months from the date the mention of grant is published in the European Patent Bulletin. Not from grant approval, not from when you noticed the patent, from that specific publication. The period cannot be extended, and the opposition is not even treated as filed until the opposition fee is paid within those nine months.

Miss it and the central route is gone. After the deadline you are left with national revocation actions, fought separately in each country, or, for patents not opted out, a central revocation action at the Unified Patent Court. Both are real options, but neither is as cheap or as clean as opposition. The practical lesson is simple: monitor competitors’ applications and diarise the grant date the moment it publishes.

Because the clock is so tight, a fast patent invalidity search in the early weeks pays for itself. You need your best prior art and arguments assembled long before month nine, not scrambled together at the deadline.

The Three Grounds You Can Actually Use

Article 100 EPC sets out an exhaustive list. You cannot oppose a patent simply because you dislike it; the attack must fit one of three grounds:

1. Lack of patentability: the invention is not new, lacks an inventive step, or covers excluded subject matter. This is by far the most common ground, usually built on prior art the examiner never saw.
2. Insufficiency of disclosure: the patent does not describe the invention clearly and completely enough for a skilled person to carry it out.
3. Added subject matter: the granted patent claims more than was disclosed in the application as originally filed.

One trap catches newcomers. Lack of clarity under Article 84 is not a freestanding ground of opposition. You can only raise clarity to the extent it bears on an amendment the proprietor makes during the proceedings. Build your case on the three grounds that count, and lead with novelty and inventive step where you can find the prior art.

Who Files, and the Case for a Straw Man

Any natural or legal person can file, with no need to show a commercial interest. That openness creates a tactical option: the “straw man” opposition, filed in the name of an attorney or a nominee so the real opponent stays hidden.

Why hide? A company may not want to reveal that it sees a rival’s patent as a threat, may be in licensing talks it does not want to sour, or may simply prefer not to invite a countersuit. The Enlarged Board of Appeal has confirmed that straw-man oppositions are allowed, provided they do not cross into abuse of process, such as a proprietor secretly opposing its own patent. Weigh the secrecy benefit against the reality that the true party is sometimes deduced anyway.

• Use a straw man when concealment genuinely protects a negotiation or commercial relationship.
• File in your own name when you want the proprietor to feel the pressure and take settlement seriously.
• Never use a nominee to disguise self-opposition or to dodge the rules on professional representation.

How the Procedure Runs, Step by Step

Opposition is adversarial but front-loaded. Everything you intend to rely on should be in your notice, because there is no US-style discovery to fill gaps later.

1. File the notice of opposition within nine months, identifying the patent, the extent opposed, and each ground with supporting facts and evidence, and pay the opposition fee (currently around 880 euros).
2. An Opposition Division of three examiners checks admissibility, then turns to the merits.
3. The proprietor gets a set period, typically four months, to respond and may defend the patent as granted or file amended claims as auxiliary requests.
4. Oral proceedings usually follow, preceded by a preliminary opinion in the summons.
5. The Division reaches one of three outcomes: reject the opposition and maintain the patent, maintain it in amended form, or revoke it entirely.
6. Any party adversely affected can appeal to a Board of Appeal, filing notice and the appeal fee within two months and the grounds within four months of the written decision.

Fees change, so confirm the current opposition and appeal figures on the EPO schedule before you budget. The Boards of Appeal sit independently of the first instance, so an appeal is a genuine fresh review, not a rubber stamp.

Opposition vs National Courts, PTAB and the UPC

Picking the forum is half the strategy. Each route has a different reach, cost and timeline.

• National revocation: available any time, even after the opposition window, but only knocks out the patent country by country. Best when you missed the deadline or care about a single market.
• Unified Patent Court: offers central revocation for patents that have not been opted out, a newer alternative to opposition worth weighing for unitary and non-opted-out patents.
• US PTAB: the closest US analogues are post-grant review, which like opposition runs on a nine-month post-grant clock, and inter partes review, which can be filed later but is limited to novelty and obviousness from documents.

Compared with the US system, EPO opposition is far cheaper, routinely allows the proprietor to amend, and involves no depositions or document discovery. If your dispute also spans the United States, coordinate timing with our guides on inter partes review strategy and USPTO vs EPO requirements so the proceedings reinforce each other instead of clashing.

Cost, Timing and Evidence Strategy to Win

Winning an opposition is mostly about the quality of your prior art and the discipline of your timing. The official fee is modest; the real budget is attorney time spent finding the document the examiner missed and framing it under the problem-and-solution approach the EPO uses to judge inventive step.

Search deep and search early. Patent literature is the obvious place, but the strongest novelty attacks often come from non-patent sources: conference papers, product manuals, standards drafts and old catalogues. Because there is no discovery, what you file is what you get, so invest in the search before you draft.

Finally, think about sequencing. If parallel proceedings are running in the US or before a national court, decide whether to lead with opposition or wait for another tribunal’s findings. A coordinated, well-evidenced opposition filed comfortably inside the nine-month window beats a rushed one every time.

How PerspireIP Can Help

An opposition lives or dies on the prior art you bring and the deadline you hit. PerspireIP runs targeted invalidity and prior-art searches, builds the novelty and inventive-step case, and helps you choose the right forum and timing. If a competitor’s European patent is in your way, talk to our team well before the nine-month window closes.

Frequently Asked Questions