Damages quantification: documents to prepare
Quantifying damages in a patent dispute requires a defined file: proof of the patent's validity period, records of the infringing use, financial statements showing lost sales or an unjustified benefit, and an expert opinion linking the figures to the infringement. Missing any of these delays the claim and weakens the number eventually presented to the deciding body.
What changes once the file is complete
A complete file changes the shape of the dispute. Before it exists, the claim states only that harm occurred. After it exists, the claim states how much harm occurred, and why that figure follows from the infringement rather than from unrelated market movements.
Courts and opposing counsel treat these two positions differently. A claim without a quantification file invites further requests for evidence and delays the hearing. A claim with a complete file moves toward a hearing on the merits of the figure itself, which is a narrower and faster argument.
The point of no return sits at submission. Once the quantification file is filed, withdrawing or materially revising the figures becomes difficult, because the opposing side has already built its response around the numbers shown. This is why the file is normally finished before filing, not adjusted afterwards.
Enforcement against the infringer is a separate stage that follows, rather than overlaps, quantification. It begins once the amount is fixed by the deciding body and runs on its own timetable. Enforcement against a holder step by step in detail sets out that later stage in a different context, though the underlying sequencing carries over: fix the amount first, enforce second.
What to do
The claimant's team, together with an instructed expert, assembles the file in a fixed order. Each step has a single clear owner, and later steps cannot start meaningfully before the earlier ones are finished.
- The patent holder gathers the registration file and confirms the validity period the claim covers.
- Counsel identifies and documents each infringing act, recording dates, volumes, and, where possible, the channel through which the infringing product reached the market.
- The company's finance team assembles supporting internal records: sales invoices, cost ledgers, and any existing licence agreements that establish a market rate.
- An accountant or retained financial expert prepares the financial basis: turnover figures, margin data, or comparable licence fees, depending on the method chosen for the case.
- An independent expert reviews that financial basis and issues a reasoned opinion connecting the figures directly to the infringement rather than to general market performance.
- Counsel compiles the whole file into a single, cross-referenced, paginated submission for the deciding body.
Documentary evidence carries more weight than testimony at this stage. Invoices, licence agreements, and accounting ledgers are harder to challenge than witness statements about lost opportunities, and the expert opinion is normally built around the documentary layer first.
Who decides
The court or tribunal already hearing the underlying infringement claim also decides the damages figure, usually after receiving expert positions from both sides. Where those positions diverge widely, the deciding body will often appoint its own expert rather than choose between the two submitted opinions.
A court-appointed review adds time to the process but produces a figure that is harder to challenge later, on appeal or in a parallel enforcement dispute. Parties sometimes accept this trade-off deliberately, to close the question of quantum for good.
When the infringement spans several jurisdictions, coordinating which forum will decide quantum becomes part of the strategy. That question is better settled before the file is finalised than argued afterwards, once positions have hardened.
| Stage | Typical documents | Approximate timing |
|---|---|---|
| Establishing the infringement basis | Registration file, evidence of infringing acts | Runs alongside the main claim |
| Building the financial basis | Turnover records, margin data, licence comparables | Four to eight weeks once instructed |
| Independent expert review | Reasoned expert opinion | Six to twelve weeks, method-dependent |
| Court-appointed review, if ordered | Second expert opinion | A further two to four months |
| Decision on quantum | Reasoned ruling of the deciding body | Follows the last expert step submitted |
Development branches
If the infringement is ongoing rather than concluded, the file must separate past harm from projected future harm. The two are usually quantified by different methods, and mixing them in one figure tends to weaken both.
If the other side disputes the financial basis rather than the underlying infringement, the case typically moves straight to a court-appointed expert, skipping a further exchange of competing figures between the parties.
If the infringer holds no recoverable assets in the relevant jurisdiction, quantification still proceeds as planned, but enforcement planning should start earlier than usual, running in parallel rather than only after the figure is fixed.
If the parties reach a settlement before the expert stage concludes, the quantification file is not wasted. It becomes the basis for the settlement figure, and courts generally accept a settlement built on a documented calculation faster than one built on an unexplained round number.
What this page does not cover
This page describes the sequence and the file, not the calculation method itself. The choice between a lost-profits approach and a licence-fee approach depends on facts this page cannot anticipate, including the size of the market and whether a comparable licence already exists.
It also does not cover recovery of legal costs, which is normally decided separately from the damages figure and follows a different procedure.
It does not cover the distinction between direct and contributory infringement either, though that distinction can change which financial records are relevant to the file in the first place.
If the infringer is registered abroad, a preliminary check such as Counterparty in Czechia in practice can confirm who is legally liable before the file is built, which avoids quantifying damages against the wrong party.
For typical turnaround across comparable files, see Delivery statistics, published automatically overview and its limits.
Verified
This page was last reviewed on 2025-01-15. It reflects procedural practice observed across comparable patent disputes, without reference to a specific statutory provision, since no such reference has passed internal verification for this jurisdiction at the time of writing. The review is repeated whenever the underlying procedure changes materially.
FAQ
How long does damages quantification take in practice?
Building the financial basis and obtaining the first expert opinion typically takes ten to twenty weeks. A court-appointed second opinion, if one is ordered, adds a further two to four months before the deciding body rules on quantum.
Which documents are needed to start?
Work can start once the registration file, a record of the infringing acts, and access to the relevant turnover or licence data are available. The expert opinion is built on top of these three, not before them.
What happens if the other side does not respond?
Silence does not stop the process. The deciding body can proceed on the claimant's figures alone, though it may still order its own expert review before accepting them as final.
Related process guides
Protective letter step by step covers a related preparatory step that some claimants complete before quantification begins.
Next steps
If the dispute also touches who owns the underlying code, When a contractor claims ownership of the code step sets out that separate track.
If a licence was involved and a sublicence appeared without consent, When a sublicence appears without consent in detail explains the first moves in that scenario.