Main infringement action: costs drivers
A main infringement action runs on four cost drivers, not one lump sum: how many claims and defendants are joined, how much technical evidence needs expert input, whether the other side counterclaims for invalidity, and how long the case runs before a settlement window closes. Each driver adds a procedural step, not just extra pages of argument.
What changes once the claim is filed
Filing fixes a procedural clock. From that point, both sides work to forum-set windows for pleadings, evidence exchange and expert reports. An injunction risk becomes live rather than theoretical, because the forum can grant interim relief once the claim is properly before it. Settlement leverage shifts too: once a defence is filed and a counterclaim for revocation is on the table, withdrawing without cost consequences becomes harder for either side.
The practical effect is that early decisions — which claims to plead, which evidence to lead first, whether to seek interim relief — set the cost profile for everything that follows. A narrow claim with clean documentary evidence moves faster and costs less than a broad claim resting on technical testimony.
| Stage | What drives cost here | Typical timing factor |
|---|---|---|
| Filing and service | Number of defendants, jurisdictions to serve | Sets the procedural clock for the whole action |
| Defence and any counterclaim | Whether validity is challenged alongside infringement | Splits the case into two parallel tracks if revocation is raised |
| Evidence and expert reports | Technical complexity of the invention, volume of disclosure | Usually the longest single stage |
| Interim relief, if sought | Urgency argument, strength of prima facie case | Runs on its own short timetable, separate from the main hearing |
| Main hearing and decision | Number of issues left unresolved by that point | Fixed once the forum sets a hearing date |
Steps to take once infringement is identified
- Instruct your patent attorney to map the claim against the alleged infringing product or process before anything is filed.
- Have litigation counsel confirm the forum and the defendants to be joined, since adding a party later reopens service and pleading deadlines.
- Preserve technical evidence — source files, manufacturing records, prior correspondence — before the other side is on notice.
- Decide early whether interim relief will be sought; the evidence bar for urgency is higher than for the main claim.
- Instruct an independent technical expert only once the claim is settled in its final form, to avoid a report that no longer matches the pleaded claim.
- Keep a running log of costs incurred at each stage — it is needed later regardless of outcome.
Who decides and by when
A specialised patent forum hears the action, not a general civil court in most cases. The forum sets its own timetable for defence, evidence exchange and any counterclaim, and that timetable is fixed once issued rather than negotiated stage by stage. A panel, rather than a single judge, typically decides technically complex disputes, which is one reason hearing dates are set well in advance and rarely moved.
Where interim relief is sought, a different and much shorter timetable applies, decided ahead of and independently from the main hearing.
Common branches
If the dispute also involves a question of who owns the underlying invention, that ownership question needs resolving before infringement can be argued on the merits — the two cannot run in parallel indefinitely. See When a development partner claims joint ownership explained for how that plays out.
If the right in dispute is recorded on a distributed ledger or a tokenised registry rather than a conventional register, proving unbroken title becomes a separate evidentiary track that has to close before the infringement claim can rely on it. That track follows its own stages and deadlines, set out in Chain of title reconstruction on-chain step by step explained.
If the other side files a counterclaim for revocation, expect the timetable to split: the infringement question and the validity question proceed on linked but separate schedules, and a decision on one can moot the need for a decision on the other.
Where this page stops
This page covers the sequence, the decision points and what drives the timetable. It does not tell you whether a specific product infringes a specific claim — that depends on the patent's wording and the accused product, and needs a claim-by-claim comparison outside the scope of a procedural overview. It also does not cover background verification of an unfamiliar opposing party or licensee, which sits with a separate part of the practice: see Counterparty in Ireland in practice for what can be established there.
Checked
Checked: 4 February 2025. This page describes the current sequence of a main infringement action as run through the competent patent forum, based on published procedural guidance and case-management practice rather than statutory citation — procedural pages on this site are scoped that way deliberately. Site-level settings such as tracking are handled separately: see Cookies and what is switched off by default step.
Related reading
If the first-instance decision does not settle the matter, the next procedural stage has its own timetable and its own cost drivers: Appeal against a first instance decision step by step.
Other deadlines you may be running at the same time
An infringement dispute rarely arrives alone. If a related mark is under opposition, that deadline runs independently and does not pause for the patent action: When an opposition deadline is running: what it costs. If the underlying licence never fixed a territory, that gap tends to surface exactly when enforcement starts: When the parties never agreed the territory in practice.
FAQ
How long does main infringement action take in practice?
Length depends on the number of issues left open by the hearing date, not on a fixed statutory figure. A claim limited to infringement, with no counterclaim and no interim relief application, moves through defence, evidence and hearing on one continuous track. Adding a revocation counterclaim or an interim relief application adds a parallel track and extends the overall timetable.
Which documents are needed to start?
At minimum: the patent itself with its claims, the evidence identifying the alleged infringing product or process, and any correspondence already exchanged with the other side. Manufacturing or technical records supporting the comparison between claim and product are gathered next, once the claim as pleaded is fixed.
What happens if the other side does not respond?
Silence does not stop the timetable. The forum sets a fixed window for a defence to be filed, and once that window closes without a response, the claimant can apply to move the action forward without waiting for the other side to engage.