EPOObservations & Oppositions builder

Intervention of the assumed infringer

Art. 105 EPC

Lets someone sued on a European patent join a pending opposition or appeal and be treated as an opponent. It must be filed within three months of the first qualifying court action.

Start an invalidity search How IPtorch builds it
Infringement action 3 months from being sued EPO Patent in opposition Novelty Art. 54 EPC Inventive step Art. 56 EPC Sufficiency Art. 100(b) EPC Added matter Art. 100(c) EPC
Inside the window, every ground tied to the patent.

At a glance

3 months from being sued

EUR 880 opposition fee, code 010 (checked 22 Sep 2026)

Who can file
A third party sued for infringement, or that sued for non-infringement after a request to cease. A separate legal entity from every opponent.
Deadline
Three months from institution of the first qualifying proceedings (Rule 89(1) EPC). No extension.
Official fee
EUR 880 opposition fee, fee code 010, within the three months. No appeal fee at the appeal stage.
Language
English, French or German. Court documents proving the litigation may stay in the court's language.
Anonymous
No. The intervener must be identified in the same way as an opponent.
Representation
Compulsory only if the intervener has no residence or principal place of business in a contracting state.
How it is filed
As an opposition: Online Filing 2.0 (EP 2300), Contingency Upload Service, or post. Not fax.
Party status
Treated as an opponent. At first instance it may continue alone (G 3/04); on appeal, a party but not an appellant.

What it is

Intervention of the assumed infringer, in brief

If you have been sued for infringement, or sued for a declaration of non-infringement after the proprietor asked you to stop, you can join someone else's pending opposition or appeal within three months. An admissible intervention is treated as an opposition, and any Art. 100 EPC ground can be raised, including a fresh one.

It cannot open or revive proceedings. The admission case (pending proceedings, qualifying event, earliest trigger, identity) cannot be cured later. An intervener that joins only on appeal becomes a party but not an appellant (G 2/24).

Grounds it can carry

  • Lack of noveltyArt. 100(a) with Arts. 52(1) and 54 EPC
  • Lack of inventive stepArt. 100(a) with Arts. 52(1) and 56 EPC
  • Not patentable on other groundsArt. 100(a) with Art. 52(2), 52(3), 53 or 57 EPC
  • Insufficiency of disclosureArt. 100(b) EPC
  • Added subject-matterArt. 100(c) EPC

Use it when

  • You were sued on the patent, or sued for non-infringement after a request to cease, while an opposition or appeal is pending.
  • The opponent may settle, withdraw or run a weak case: a first-instance intervener can continue alone (G 3/04).

Choose another route when

How IPtorch builds it

From search to filing, minus the signature.

The invalidity search runs on into this filing when it ends, with no second click. Three model families take turns, so a draft is never checked by the model that wrote it.

  1. 1SearchClaims split into limitations, thousands of candidates screened, at least 50 references read in full.Gemini models read and check
  2. 2Claim mapA verbatim quotation and its location behind every limitation.Every cell checkable
  3. 3DraftWrites the papers in the office's format and language.Claude Opus 5.5 (Anthropic)
  4. 4ReviewChecks each citation against its document and builds the forms.Sol 6 (OpenAI)
  5. 5AdjudicateHigh strength: a third family rules on every objection.Gemini 3.1 Pro (Google)
  6. 6FolderUnsigned PDFs, ready for a professional to review, sign and file.Nothing is filed

What the builder does for this filing

  • It refuses the job before any spend if the intervener's name and address are missing, because an intervention cannot be anonymous.
  • It drafts the admissibility case first: the limb relied on, the court, case number, institution and service dates, the three-month computation from the earliest qualifying proceedings, and the pending proceedings.
  • It adopts the opponent's submissions expressly, by party and date (T 1659/07), and adds its own Art. 100 grounds from an invalidity search of at least 50 references read in full, each re-qualified under the EPC's prior-art rule and pinpointed.
  • It rejects a warning letter or evidence preservation as the trigger, flags a UPC action as an unsettled trigger, and never instructs an appeal fee at the appeal stage.

In the folder

  • Notice of interventionDeclaration on page 1, admissibility first, then the grounds
  • Exhibit listAdmissibility exhibits, substantive documents and submissions adopted
  • Admission moduleInternal: chronology, qualifying event, three-month computation, proof map
  • Identity and succession recordInternal: the intervener is the litigant or its successor
  • Form 2300 field valuesOnly if the statement is filed with Form 2300
  • Copies of every cited documentCourt documents and prior art, each numbered as an exhibit
  • Labelled machine translationsBeside the original, including quoted court passages

Builder strength

You choose how hard it is checked.

You pay for the tokens the sessions use, at the models' list prices plus a 30% fee, not for the time allowed. How pricing works

Low

40 minutesabout 10 million tokens (roughly $10 to $30)

  1. Opus 5.5 drafts the submission
  2. Sol 6 builds and checks the final forms

Medium

2 hoursabout 20 million tokens (roughly $20 to $60)

  1. Opus 5.5 drafts the submission
  2. Sol 6 reviews and rebuilds the content
  3. Opus 5.5 builds the filing folder
  4. Sol 6 checks the form

High

5 to 6 hoursabout 60 million tokens (roughly $50 to $200)

  1. Opus 5.5 drafts the submission
  2. Sol 6 runs a deep prior-art search
  3. Opus 5.5 rebuilds the submission against the evidence
  4. Sol 6 attacks it as an adversarial examiner
  5. Gemini 3.1 Pro adjudicates the objections
  6. Opus 5.5 applies the fixes and builds the filing folder
  7. Scripted checks of the filing folder
  8. Sol 6 audits the whole folder
  9. Convergence gate

If the gate fails, one repair round: opus 5.5 repairs what the gate found, sol 6 audits the repair, convergence gate, again.

What stays with you

You review, sign and file.

  • Litigation counsel supplies the complaint and the court's record of institution and service.
  • An officer or representative signs, stating capacity for a legal person.
  • Pay EUR 880 within the three months by debit order, card or transfer.
  • File through Online Filing 2.0 or on paper and keep the receipt.

Where these go wrong

What the builder guards against.

  • Running the three months from the wrong event: the period runs from the first qualifying proceedings, not a later action (T 296/93).
  • Relying on a warning letter or evidence preservation: neither is a qualifying event (T 195/93).

More filings in Europe

EPO, UPC and national courts

All 17 filings

Start with the evidence.

Upload the patent or enter its number. The invalidity search charts every claim, and the builder takes it from there.

Start an invalidity search

Facts checked against the office's rules on 22 September 2026. IPtorch is not a law firm and this page is not legal advice. The builder's output is unsigned work product for a registered professional to review, sign and file; nothing is filed and no fee is paid for you. Confirm current requirements, fees and deadlines with the receiving office.