Protective letter: stages and deadlines
A protective letter is a pre-emptive submission filed with a court before any injunction request reaches you. It explains in advance why an urgent, one-sided order would be wrong. Once lodged, it stays with the court and surfaces automatically if the other side later asks for immediate relief. Filing after such an order is granted removes that chance entirely.
What changes once a protective letter is filed
Before filing, an opponent who wants an urgent injunction can ask a court to decide without hearing you at all. Courts that allow this route usually do so because the applicant claims surprise or urgency justifies acting fast. A protective letter removes that surprise. The court sees your side of the argument the moment it looks at the file, even though no hearing has been scheduled and no claim has formally been served on you.
The practical effect is procedural, not substantive. A protective letter does not settle the underlying patent dispute, and it does not stop the other side from suing you through ordinary channels. What it changes is the odds that a court grants an order against you without asking a single question first.
Stages, in order
| Stage | What happens | Typical timing |
|---|---|---|
| Risk assessment | You identify a live threat of an urgent injunction request against you | Before any claim is served |
| Drafting | Legal and technical arguments against the anticipated order are set out | A few working days, depending on complexity |
| Filing | The letter is lodged with the court likely to receive the injunction request | Same day as completion |
| Docketing | The court registers the letter against the parties and the patent named in it | Handled by the registry on receipt |
| Dormant period | The letter sits in the file, unseen by the other side, until a request for relief arrives | Open-ended, often months |
| Activation | An injunction request is filed; the court opens the protective letter automatically | At the moment of the request, not before |
The point of no return sits at the activation stage. Once a court has already granted an ex parte order, a protective letter filed afterwards has nothing left to prevent. Its entire value depends on being on file before the request for relief lands.
Documents you need before you file
A workable protective letter rests on a narrow set of materials, gathered before drafting starts:
- Identification of the patent or patents at risk, including the granting authority and status.
- A description of your product or process, precise enough to show why it does not infringe, or why the patent is vulnerable.
- Any prior correspondence with the opposing side, including warning letters or cease-and-desist demands.
- Evidence supporting your defence: technical opinions, prior art, or licence documentation, as relevant.
- Confirmation of which entity or entities are named or likely to be named as defendants.
Where the underlying dispute also touches ownership of design or content files rather than the patent itself, the ownership question usually runs on a separate track: Media, content and streaming an agency keeps the design sets out how that is typically resolved.
What to do
- Confirm, with counsel, that an urgent injunction request is a realistic near-term threat, not a distant possibility.
- Assemble the technical and documentary file described above before any drafting begins.
- Instruct counsel to draft the letter addressing both the merits and the absence of urgency, where that argument applies.
- File the letter with the court most likely to receive the injunction request, not a court chosen for convenience.
- Confirm docketing with the court registry rather than assuming the filing was recorded correctly.
- Monitor the matter and refresh the letter if the underlying facts or the patent's status change materially.
Who decides, and how quickly
The letter goes to the same court that would receive an urgent injunction application in the underlying dispute. That is usually the forum handling the infringement matter itself, whether the case sits at national level or, depending on how the patent was granted, at a supranational forum. There is no separate hearing on the protective letter alone: it is read only if and when the other side asks for urgent relief, and the court then decides the injunction request with the letter already in view.
Common scenarios
If you have already received a warning letter naming a specific patent, filing without delay matters more than filing a longer document. A short, well-targeted letter beats a comprehensive one that arrives too late.
If the threat is speculative and no warning letter exists yet, weigh the cost of drafting against the likelihood the other side moves quickly. Some businesses file anyway once a competitor patent issues in a contested area.
If your dispute also involves digital content that references a third party's work, and that content is later taken down, the exposure runs on its own track: When the referenced work is removed in detail covers what that costs when the assumption behind it turns out wrong.
What this page does not cover
This page describes the stages and timing of a protective letter itself. It does not cover how a claim or an injunction request is served on a defendant once proceedings start, which follows separate rules: Cross-border service of documents step by step addresses that step on its own.
It also does not cover the substance of infringement or validity arguments, drafting standards for the letter itself, or fee levels for filing. Those depend on the specific court and the specific patent, and are not addressed here.
Verified
This page describes general procedural practice around protective letters and does not itself verify facts about a named opponent. Where the other side is registered outside the EU, checking what a public register can actually confirm matters before you rely on it: Counterparty in Hong Kong in detail sets out what such a register shows and where it stops.
Details on how information shared with us during this process is handled sit in a separate document: Data processing agreement and its limits.
Next step
If your situation already involves a licence with field-of-use restrictions that the other side appears to be ignoring, the immediate steps differ from those above: When field-of-use limits are ignored explained sets out what to do first.
FAQ
How long does a protective letter take in practice?
Drafting typically takes a few working days once the underlying file is complete. Filing itself is quick; the letter then sits with the court, sometimes for months, until an injunction request arrives.
Which documents are needed to start?
At minimum: identification of the patent at risk, a description of your product or process, any prior correspondence with the opposing side, and supporting technical or licensing evidence.
What happens if the other side does not respond?
Nothing happens automatically. The letter remains on file, unused, until an injunction request is filed. If none ever arrives, the letter simply expires in relevance rather than being formally withdrawn.