Main infringement action: what the other side does
Once a patent infringement claim is served, the other side has a fixed window to respond. It reviews the claim, decides whether to contest infringement, validity, or both, and files a formal defence with the court. Silence is rare; the more common move is a mix of denial and counterattack.
What changes once the claim lands
Service of the claim starts the clock on both sides. The claimant now has a filed position it cannot quietly withdraw without cost consequences, and the defendant has a deadline that does not move for convenience. From this point, correspondence between the parties tends to slow down, because anything said outside the court file can be used against its author later. Settlement talk does not stop, but it moves behind the case rather than instead of it.
The practical risk shifts too. Before service, the main exposure was uncertainty about whether a claim would be brought at all. After service, the exposure is procedural: missed deadlines, incomplete filings, and evidence gaps become the live issues, not the underlying dispute about the patent itself.
What the other side typically files
| Stage | What happens | Typical window |
|---|---|---|
| Acknowledgement | Confirms receipt of the claim and, in most fora, an intention to defend | Days, not weeks |
| Statement of defence | Sets out denial, admission, or partial admission of the alleged infringement | Weeks after service |
| Counterclaim for invalidity | Challenges the patent itself rather than only the alleged infringing act | Filed together with, or shortly after, the defence |
| Request for particulars or extension | Asks for more detail on the claim, or more time to respond | Early, before the defence is due |
| Application for interim measures | Either side may seek a temporary order pending trial | Can arise at any stage |
A counterclaim for invalidity is the move that changes the shape of the whole case. Once validity is on the table, the dispute is no longer only about what the defendant did — it is also about whether the right being enforced can survive scrutiny at all.
What to do on the claimant side
- Confirm service was valid and keep proof of the date, since every later deadline runs from it.
- Read the defence line by line and separate genuine denial from procedural stalling.
- If a counterclaim for invalidity appears, brief counsel immediately — it usually reshapes the evidence plan.
- Track every deadline in a single calendar shared with the litigation team, not in email threads.
- Preserve internal records of the invention and its use before anyone is asked to disclose them.
- Decide early whether interim relief is worth pursuing, since delay weakens that argument on its own.
Who decides, and on what timeline
The forum handling the dispute manages the calendar from the first filing onward. A judge or panel assigned to the case — often called a case management judge in this type of dispute — sets deadlines for the defence, any counterclaim, and the exchange of evidence. Interim applications are usually decided by the same forum on a shortened timetable, sometimes within weeks, because delay defeats their purpose. The main action itself, from service to a first-instance decision, commonly runs well beyond a year once evidence, expert input, and a hearing are factored in.
Ownership questions that surface mid-case
Defences sometimes reach further back than the alleged infringing act. If the underlying invention passed through more than one pair of hands before the patent issued, the other side may ask who actually owned the right to file at all. This is a distinct dispute with its own logic — When a founder leaves with the prototype in detail sets out how that question is usually resolved when it surfaces separately from litigation.
Licensing gaps that turn into infringement disputes
A common variant of the defence is that the alleged use was licensed, or fell within a wider commercial agreement covering the technology. Where the underlying deal touched tokenised or smart-contract-based licensing arrangements, the paperwork trail matters more than usual, because the terms are often distributed across several documents rather than one signed agreement. Smart contract and licence alignment step by step explained covers what that document set should contain before a dispute forces the question.
Three scenarios worth naming in advance
- If the other side files nothing by the deadline, the claimant can usually apply for a default judgment, but the application still has to prove the claim was properly served and the substance is made out — a missed deadline is not, on its own, proof of infringement.
- If the defence includes a counterclaim for invalidity, expect the case to split into two tracks running in parallel, with the invalidity question sometimes resolved before the infringement question is reached.
- If the other side seeks an extension early, this is routine and rarely refused outright, but a pattern of repeated extension requests is worth flagging to counsel as a possible delay tactic.
Evidence disclosure and personal data caught in the file
Disclosure obligations during a main infringement action can pull in documents that contain personal data — employee correspondence, supplier records, or engineering logs with named individuals. Handling those documents inside the litigation file does not remove the separate rights individuals hold over their own data. If you are named in a report explained covers what happens when someone asks about their personal data appearing in material connected to a dispute.
What this page does not resolve
This page describes the procedural sequence after service — what filings to expect, in what order, and on what kind of timetable. It does not assess the merits of a specific claim, does not estimate the strength of a validity challenge, and does not set out the evidence needed to prove infringement in a particular technical field. Those questions depend on the patent, the alleged use, and the forum, and need a file-specific review rather than a general procedure.
Verified
Reviewed for accuracy against current procedural practice at the time of publication. Primary reference: the published procedural rules of the forum handling the dispute, which set the applicable deadlines and filing requirements in each case. Where the underlying dispute also involves a counterparty relationship that predates the litigation, a separate check is often useful — Counterparty report before onboarding a distributor explained covers what to verify about the other side before a commercial relationship, rather than a dispute, begins.
FAQ
How long does a main infringement action take in practice?
From service of the claim to a first-instance decision, the action commonly runs beyond a year once evidence exchange, expert input, and a hearing are scheduled. A counterclaim for invalidity typically extends this further.
Which documents does the other side need to respond?
At minimum, an acknowledgement of the claim and a statement of defence. Where invalidity is contested, a formal counterclaim with supporting evidence follows, usually on the same or a closely linked timetable.
What happens if the other side does not respond?
The claimant can usually apply for a default judgment, but the court still checks that service was valid and that the claim is properly made out — a missed deadline shortens the process without removing the need to prove the case.
Related publications
Appeal against a first instance decision step by step covers what happens once a first-instance decision in this type of action is challenged.
Next step
If the dispute reaching you involves rights already pledged or licensed to a third party, the enforcement questions run in parallel to the infringement action rather than instead of it — When a pledge over rights is enforced explained sets out what to check first.