Main infringement action: what the decision maker looks at
A decision maker in a main infringement action looks at three things: whether the patent is valid, whether the accused product or process falls within the scope of its claims, and whether the timeline of use supports the claim as filed. Every document in the file exists to answer these three questions clearly, and to answer them early rather than late.
How the stages unfold
The action moves through a fixed sequence, whatever the forum. The order rarely changes. What changes is how long each stage takes, and that depends on how contested the technical facts turn out to be.
| Stage | What happens | What tends to lengthen it |
|---|---|---|
| Filing | The claimant lodges the statement of claim together with the evidence it already holds. | Claim charts that are thin or poorly mapped to the accused product |
| Response | The defendant files a defence, often paired with a counterclaim challenging validity. | A parallel invalidity attack, which widens the file well beyond the original claim |
| Evidence exchange | Both sides submit technical evidence, expert opinions and, where relevant, physical samples. | Evidence sitting in more than one jurisdiction, which needs translation and certification |
| Hearing | The decision maker questions the parties and their technical experts directly. | Several experts on each side, each needing separate time on the record |
| Decision | A written ruling covers infringement, validity and, where infringement is found, remedies. | A claim construction dispute that has to be resolved before remedies can be assessed |
Nothing in this sequence is optional. A stage can be shortened by good preparation, but it cannot be skipped.
What the decision maker actually examines
Validity comes first, because an invalid patent cannot be infringed. The decision maker checks whether the claims, read in light of the prior art on file, still stand. This is why a defendant almost always raises invalidity alongside, rather than instead of, a denial of infringement.
Claim scope comes second. The decision maker compares the wording of each claim, element by element, against the accused product or process. A claim chart that maps this comparison feature by feature carries more weight than a general description of similarity.
Timeline comes third. The decision maker wants to know when the alleged infringing act began, whether it continues, and whether the claimant knew about it earlier than the filing date suggests. A gap between knowledge and filing is one of the first things a defendant will raise.
Documents you need before you open the file
The file has to show ownership of the right, the scope of the claims, and the alleged infringing act, in that order. Ownership disputes surface more often than the paperwork suggests, especially where a prototype changed hands informally between colleagues or co-founders before any patent was filed. Our account of a founder who leaves with the prototype in the photonics field, Photonics and instrumentation a founder leaves with the prototype, shows how a missing assignment can stall a claim long before it reaches a decision maker.
Beyond ownership, the core set is short: the patent certificate, the claim chart against the accused product, any prior correspondence with the other side, and a record of the alleged infringing act itself, such as a product sample, a sales listing, or technical documentation obtained lawfully.
Timing and the point of no return
Once the statement of claim is served, withdrawal without cost consequences becomes difficult. This is the point of no return in the procedure, and it arrives earlier than most claimants expect.
A similar pattern shows up in a different asset class. Once a tokenised right is transferred, the issuer can lose the practical ability to reverse the transaction, whatever the contract intended. See When the issuer loses control of the contract explained for that parallel, drawn from a different area of the practice.
After filing, the pace of the action is largely set by the response, the depth of the evidence exchange, and whether either side seeks interim relief along the way.
Who decides and in what forum
Depending on the patent and the jurisdiction involved, the case goes either to a national civil court or to a panel of the Unified Patent Court. The forum is fixed by the nature of the right in dispute, not by either party's preference.
A panel typically includes a legally qualified judge and, where the dispute turns on complex technology, a technically qualified judge as well. The presence of a technical judge changes how evidence is questioned at the hearing, and often shortens the time needed to reach a decision on claim scope.
Common forks
If the other side does not respond within the set period, the claimant can ask for a ruling on the record already filed, without waiting for a defence that never arrives.
If the infringement is ongoing and urgent, a separate application for interim measures runs alongside the main action, rather than replacing it.
If the relevant evidence sits in more than one jurisdiction, the timeline stretches to allow for cross-border requests, and this should be planned for from the first filing.
Related publications
The stage after a first-instance ruling is covered separately, because the questions a decision maker asks on appeal are not the same as the ones asked at first instance: Appeal against a first instance decision step by step sets out what changes once a ruling exists.
What this page does not cover
This page does not cover the cost of a main infringement action, the specific forms required in any one national forum, or how evidence is collected before a claim is filed. It also does not cover settlement strategy, which depends on facts this page cannot see. Those questions sit elsewhere, and answering them here would only blur the procedure this page is meant to explain.
Sources and the limits of this account
This account describes the procedure at a general level. It does not cite specific statutory articles, because the applicable national implementing rules vary by forum and are outside the scope of this note. Where a dispute also involves a counterparty whose registered details have changed since the original contract was signed, a separate check is often needed first: Counterparty report when the counterparty changes name explained covers that step in detail.
This account was last reviewed on 10 March 2025 and was compiled by the team described at The people behind the reports explained.
What drives the cost, and how fast we respond
Four factors drive the cost of a main infringement action: the number of jurisdictions involved, whether the other side raises a parallel invalidity attack, whether interim relief is sought alongside the main claim, and how many technical experts the dispute requires. None of this is priced in advance, because each factor changes the shape of the file before work even starts.
A partner replies within minutes during working hours. A price follows within one working day, once the file has been reviewed.
Frequently asked questions
How long does main infringement action take in practice?
The length depends on how contested the technical facts are, not on a fixed calendar. A file with a clean claim chart and an uncontested timeline moves faster than one with a parallel invalidity attack and evidence spread across jurisdictions.
Which documents are needed to start?
The core set is the patent certificate, a claim chart mapped against the accused product, a record of the alleged infringing act, and proof of ownership of the right. Ownership proof matters most where a patent followed an informal handover of a prototype.
What happens if the other side does not respond?
The claimant can ask the decision maker for a ruling based on the record already filed, rather than waiting indefinitely for a defence. The other side keeps the right to challenge that outcome later, within the limits the forum sets for doing so.