When prior art surfaces after grant: what to do first
When prior art surfaces after grant, the patent is not automatically invalid. It stays enforceable until an authority revokes or narrows it. Days matter because a limitation period on the challenge you intend to use may already be running. Freeze the evidence, record the discovery date, and take advice before the other side does.
Basis
For a European patent with unitary effect, one forum decides validity across every participating state at once. The Agreement on a Unified Patent Court gives the Unified Patent Court jurisdiction over actions for revocation, alongside actions for infringement. Regulation (EU) No 1257/2012 sets out which granted patents fall within that unitary regime in the first place.
The regime covers patents that were granted through the ordinary examination route and then registered with unitary effect afterward. The grant procedure itself is a separate question, and this page assumes grant has already happened and the prior art surfaced afterwards.
Outside the unitary regime, the same challenge runs before the national court or the office that granted the patent, under that office's own procedure. This page does not track individual national rules; it sets out the sequence that applies before you reach that stage.
What changes in practice
Prior art found after grant does not annul the patent by itself. Someone still has to bring a challenge, and that challenge has a clock attached to it. The clock usually starts from when the prior art was published, not from when you happened to find it. Waiting to confirm the finding is not the same as waiting at no cost — every day spent confirming is a day already counted against whichever deadline applies.
Depending on how much time has passed since grant, the available channel differs: a still-open, opposition-type window at the granting office, or a stand-alone revocation action once that window has closed. Which one is open in your case sits in the file, because the exact cut-off is set by the granting office's own rules, not by this page.
A second consequence is evidentiary. Once you raise prior art, the patent holder gets a chance to argue that the document does not, in fact, anticipate the claims — through a different reading of the claims, an earlier priority date, or a technical distinction you missed. Prepare the comparison as if it will be contested, because it will be.
What to do first
Forum follows two facts, and both sit in the patent's own file rather than in the prior art itself: whether the patent carries unitary effect, and whether it has been opted out of the Unified Patent Court's jurisdiction. Confirm both before choosing where to file.
- Legal counsel: freeze and date the prior art find — save the document itself, its publication date, and where you found it, before discussing it with anyone outside the file.
- Patent attorney: compare the prior art against the granted claims, claim by claim, and mark which claims it reads onto and which it does not.
- In-house team: check whether the patent has already been asserted against you, licensed to you, or is subject to a standstill — this changes how urgently you need to move.
- Counsel: identify the correct forum — the office that granted the patent, the national court, or the Unified Patent Court if the patent carries unitary effect.
- Decision-maker: decide whether to raise the prior art defensively, as a shield if you are sued, or offensively, to clear a patent that blocks you.
- Filing team: prepare the submission against the earliest deadline in play, not the most convenient one.
Who decides
| Situation | Forum | What is decided |
|---|---|---|
| European patent with unitary effect | Unified Patent Court, under the Agreement on a Unified Patent Court | Validity of the patent as a whole, including revocation |
| European patent not opted out, within the transitional period | Unified Patent Court or the national court, depending on the patent holder's choice of forum | The same claims, in either forum |
| National patent outside the unitary system | The national court, or the national office that granted the patent | Validity under that office's own procedure |
Depending on your situation
- If the patent is a European patent with unitary effect: the challenge goes to the Unified Patent Court under the Agreement on a Unified Patent Court, and one ruling covers every participating state.
- If the patent was opted out of Unified Patent Court jurisdiction while that option was still open: the challenge stays with national courts, and a ruling only binds that one jurisdiction.
- If the prior art was already before the examiner during grant and simply overlooked: challenging the patent on the same reference is harder, because the granting office is presumed to have considered it — build the challenge around a fact the examiner did not have.
- If the prior art surfaces while you are already being sued for infringement: raise it as a defence inside that case rather than opening a separate revocation action, and confirm with counsel that the forum allows this.
Ownership questions sit next to validity questions but are decided on different evidence. Where the dispute is about who owns the invention rather than whether it is valid — for instance when the founding contract is silent on assignment — the procedure runs separately: What to do first in this situation step by.
The same timing logic applies wherever a prior right predates your own, including outside patents. In digital collections, the equivalent problem is covered in When a collection uses third-party artwork explained.
What this page does not solve
This page does not tell you whether the prior art actually destroys novelty or inventive step — that is a technical comparison for a patent attorney, not a procedural question. It also does not tell you whether the challenge is worth the cost relative to the patent's commercial value; that is a business judgement, made once the forum and deadline are already fixed.
It does not establish who else might hold a competing right over the same invention, or whether a counterparty abroad has clean title to license it. That is a factual question answered by due diligence, not by this page: see Counterparty in Switzerland step by step for how such a check is structured.
Related situations
A related timing problem arises when a joint development partner files alone on a shared result: When a joint development partner files alone in practice.
Checked
Checked on 4 March 2025 against the Agreement on a Unified Patent Court and Regulation (EU) No 1257/2012. Data handling during a review is described in our Privacy notice: two roles, two bases step by step.
Frequently asked questions
What is the first step when prior art surfaces after grant?
Freeze the prior art itself — save the document, note where you found it and its publication date — before taking any other step. That record becomes the evidence for whichever forum eventually decides the challenge.
Which deadline is already running?
At least one limitation period starts to run from when the prior art was published, not from when you found it. Which period applies depends on the forum and the type of challenge, so treat every day as chargeable until counsel confirms otherwise.
Who decides, and on what evidence?
For a European patent with unitary effect, the Unified Patent Court decides, under the Agreement on a Unified Patent Court, on the evidence both sides submit — chiefly the prior art document and an expert comparison against the granted claims.