Opposition before the granting office: what the other side does
Once a patent application is published, a third party can file opposition before the granting office to block or narrow the grant. The other side's task is procedural, not creative: file within the window, back the challenge with prior art or formal grounds, and respond to every deadline the office sets. Miss one deadline, and their opposition typically fails without a hearing on the merits.
What opposition before the granting office actually is
Opposition is a formal challenge lodged with the same office that is due to grant, or has just granted, the patent. It runs on paper first: written submissions, evidence bundles, and office communications with fixed response periods. A hearing only happens if the written stage leaves open questions the office cannot resolve on the file alone.
The office does not investigate on its own initiative. Everything that reaches the file — prior art, expert statements, procedural objections — comes from the parties. This is why what the other side files, and when, decides most of the outcome long before any hearing date is set.
What changes in your timeline and risk
Once opposition is filed, the application or the granted patent enters a holding pattern. Licensing talks stall, because a counterparty will not commit to a patent whose validity is contested. Enforcement against a third infringer is usually paused, since a patent under active challenge is a weak basis for a claim.
The clock also changes shape. Instead of one filing deadline, you now face a sequence of response windows set by the office, each with its own consequence for missing it. A single missed window can end the case in the other side's favour, or in yours, depending on who misses it.
What the other side typically does
| Stage | What the other side does | What it triggers for you |
|---|---|---|
| Filing | Submits the opposition within the office's window, naming the grounds | Your file is now contested; internal notice period starts |
| Evidence | Files prior art, technical opinions, or formal defect claims | You must review and prepare a substantive reply |
| Office communication | Responds to office queries within the set period | Silence on their side can narrow or end their case |
| Reply round | Comments on your response, sometimes narrowing the attack | The scope of the dispute is set for any hearing |
| Hearing or decision | Argues orally, or lets the written file stand | The office decides on the file as it stands at that point |
The pattern that matters most: opponents who file broad grounds early but then go quiet at the evidence stage are common. Their opposition usually narrows or lapses at that point, and the applicant's task shifts from full defence to confirming the lapse.
What to do
- Log the opposition date the moment notice arrives; every later deadline runs from it.
- Have the file owner confirm which claims the other side is actually attacking.
- Instruct the responsible attorney to draft a substantive reply, not a holding statement.
- Track the office's response window separately from your own internal review time.
- Request an extension only through the office's own channel, before the window closes.
- Confirm receipt of every office communication in writing, on both sides of the file.
Who decides and by when
The granting office's opposition division decides on the written file, unless a hearing is requested or ordered. The decision covers the grounds actually argued — grounds raised but not pursued at the evidence stage are usually treated as abandoned. Appeal against the decision goes to the office's own appeal body, on a separate clock that starts from notification of the decision, not from the hearing date.
Two scenarios worth separating
If the other side files broad grounds but never submits supporting evidence, the office will usually decide on formal weakness alone, and the case can close faster than either side expects.
If the other side is well prepared and submits detailed prior art early, expect at least one full reply round before any hearing is scheduled, and plan the internal budget for expert input accordingly.
A related dispute arises when the client wants the design files, not just When the client wants the design files, not just the granted right — the cost and evidence picture there differs from opposition itself.
Factors that drive the effort involved
The scale of the response depends on a small set of variables, not on the size of the dispute alone: how many claims are attacked, how much prior art the other side files, whether an oral hearing is requested, and whether parallel proceedings exist in another jurisdiction. A comparable procedure applies outside patents too: Dispute over minting rights step by step in detail follows the same logic of staged written rounds before any decision-maker looks at the merits.
How the file is structured
Every opposition file we run keeps three streams separate from the outset: the office's own deadlines, the technical evidence being prepared, and internal sign-off on strategy. Keeping these apart avoids the common failure where a technically strong reply misses its window because sign-off ran late. For how personal data and evidence within the file are handled, see Privacy notice overview and the evidence.
Sources and limit
This page describes the sequence of an opposition and what the other side typically does within it. It does not set out the substantive grounds on which a patent can be revoked, and it does not cover enforcement once opposition ends — those follow their own procedure. Where the other side is a company based outside the EU, background verification of that party becomes a separate, useful step: Counterparty in United States in detail sets out what can be established and how.
Related publications
See also Revocation proceedings step by step for the parallel procedure once a patent has already been granted.
Verified
Reviewed: 2025. Sources: the granting office's published opposition guidance and our internal procedural log across current files. No article numbers or case citations are stated on this page; the underlying national implementing texts are not yet confirmed in our registry, and we do not cite what we cannot verify.
FAQ
How long does opposition before the granting office take in practice?
Timing depends entirely on how many written rounds the parties generate. A file with no hearing and a quiet opponent can close within a few months of the response windows lapsing. A contested file with expert evidence and a hearing routinely runs well beyond a year.
Which documents are needed to start?
At minimum: the published application or granted patent, the notice of opposition itself, and any prior art or technical opinion the other side has filed. Your own file should also hold every prior office communication on the case, in sequence.
What happens if the other side does not respond?
Silence within the office's response window usually works against the silent party. Grounds not maintained through a reply are typically treated as abandoned, and the office proceeds to decide on whatever remains actively argued on the file.