Letter Before Action: What to Expect in UK Patent Disputes

If you're involved in a UK patent dispute—whether enforcing your rights or facing an infringement allegation—you'll encounter the Letter Before Action. Understanding this uniquely UK procedural requirement is critical for both patent holders preparing to enforce and recipients assessing their options.

In the UK, the Letter Before Action (LBA) is not optional—it's a required pre-litigation step governed by the Civil Procedure Rules.1 This structured approach differs significantly from US cease and desist practice and sets the foundation for how UK patent disputes proceed.

What Is a Letter Before Action?

A Letter Before Action (also called a "letter of claim") is a formal written notice sent before commencing patent infringement proceedings in England and Wales.2 Under the Practice Direction on Pre-Action Conduct and Protocols, a claimant must send this letter before filing a claim at the Patents Court or Intellectual Property Enterprise Court (IPEC).3

Purpose and Legal Framework

The LBA serves several functions:4

• Provide notice: Inform the alleged infringer of the specific infringement claims
• Enable settlement: Give both parties opportunity to resolve the dispute without litigation costs
• Establish procedural compliance: Demonstrate good faith engagement required by the courts
• Create legal record: Document the parties' positions before proceedings

The legal framework governing LBAs includes:

• Civil Procedure Rules (CPR) Part 63: Intellectual Property Claims5
• Practice Direction 63A: Supplementary guidance for IP claims6
• Practice Direction on Pre-Action Conduct and Protocols: General pre-action requirements7

###How UK Differs from US Cease & Desist

While both serve to notify alleged infringers, the UK Letter Before Action operates within a structured procedural framework that doesn't exist in the US:8

Aspect	UK Letter Before Action	US Cease & Desist
Legal Requirement	Mandatory pre-action step under CPR	Optional, no formal requirement
Procedural Framework	Governed by Pre-Action Protocols	No standardized procedure
Contents	Specific requirements defined by protocol	No mandated contents
Unjustified Threats	Strict limitations on recipients (primary actors only)	Broader ability to contact customers/users
ADR Requirement	Must state willingness to engage in ADR	No formal ADR requirement
Good Faith Obligation	Parties expected to engage constructively	More adversarial approach common
Court Enforcement	Non-compliance can result in costs penalties	No procedural penalties

Strategic Implication: The UK system encourages pre-litigation resolution through structured engagement, while the US approach allows—but doesn't mandate—such discussions.9

Who Must Send an LBA (and When)

Before filing patent infringement proceedings in the Patents Court or IPEC, the claimant must send a Letter Before Action.10 This applies regardless of where litigation will be filed—both venues require pre-action compliance.

Timing

The LBA must be sent before issuing the claim form. The recipient should be given a reasonable period to respond—typically 14 days, though sometimes longer depending on complexity—before proceedings commence.11

Exceptions

The court recognises that in some circumstances it may be inappropriate to give the defendant prior notice, such as:12

• Urgent cases where immediate injunctive relief is needed
• Risk of evidence destruction where notice might prompt the defendant to destroy relevant materials
• Multi-jurisdictional races where providing notice could allow the defendant to file first in another jurisdiction

However, such exceptions are limited, and failing to send an LBA without good reason can result in adverse costs consequences.

What are adverse costs consequences?

The court will take non-compliance with pre-action protocols into account when making costs orders.13 This means the court may:14

• Order the non-compliant party to pay the other side's costs even if they win the case
• Reduce the amount of costs the non-compliant party can recover if successful
• Order costs on an indemnity basis (higher amount) rather than standard basis as a penalty
• Make costs orders at interim stages reflecting the additional expense caused by non-compliance

The specific sanction depends on the nature and seriousness of the breach, but non-compliance fundamentally affects how courts exercise their discretion on costs allocation between parties.15

Unjustified Threats: Critical Limitation on Who Can Be Contacted

One of the most important considerations when drafting an LBA is avoiding unjustified threats liability under the Patents Act 1977, Sections 70-70E.16

Primary Actor vs. Secondary Infringer

A communication contains a "threat of infringement proceedings" if a reasonable person in the position of the recipient would understand that: (a) a patent exists, and (b) proceedings will be brought for infringement.17 The test is objective—the intention of the sender is irrelevant; what matters is whether a reasonable recipient would understand it as a threat.17a

However, not all potential recipients can lawfully be threatened. The distinction turns on whether the alleged infringement constitutes a "primary act" under Section 70A(2) of the Patents Act 1977.18

Primary Actors (can be contacted without risk of unjustified threats liability):19

Under Section 70A(2), threats are not actionable when the alleged infringement consists of:

• Making a product for disposal (where the invention is a product)
• Importing a product for disposal (where the invention is a product)
• Using a process (where the invention is a process)20

Therefore, manufacturers, importers, and process users are primary actors who can be directly contacted.

Secondary Infringers (generally cannot be contacted directly):21

Threats against secondary infringers—those who sell, distribute, or use infringing products downstream—are actionable unless they fall within the "permitted communications" exception. This includes:

• Customers purchasing allegedly infringing products
• Retailers selling allegedly infringing products (including online marketplaces like Amazon)21a
• Distributors handling allegedly infringing products
• End users of allegedly infringing systems

The rationale is that patent holders should direct enforcement efforts toward the source of the infringement (manufacturers/importers) rather than disrupting downstream commercial relationships.22

Defence for Inability to Locate Primary Actor

Section 70C(4) provides a limited defence when secondary infringers are contacted:23 If the patent holder can demonstrate they took reasonable steps to identify the primary actor but could not locate them, and notified the recipient of those steps, the threat may be justified. However, if a primary actor is identified, this defence cannot be relied upon.

Consequences of Unjustified Threats

A person aggrieved by an unjustified threat can bring proceedings for:24

• A declaration that the threat is unjustified
• An injunction against continuance of the threat
• Damages for any loss sustained

This makes LBA drafting critical—poorly worded letters sent to the wrong recipients create significant liability for the patent holder.

What Must Be Included in an LBA

While there is no specific pre-action protocol dedicated solely to patent litigation, the general Pre-Action Conduct Practice Direction and established practice define what an effective LBA must contain.

Required Contents

Based on procedural guidance and legal practice, a comprehensive LBA should include:25

1. Patent Identification

   • Patent number and title
   • Confirmation of ownership, assignment, or exclusive license status
   • Relevant claims allegedly infringed

2. Description of Alleged Infringement

   • Specific products, processes, or services allegedly infringing
   • When the infringing activity began (earliest evidence date)
   • How the patent claims map to the accused implementation

3. Evidence of Infringement

   • Sample product (or details of where it can be inspected)
   • Screenshots, specifications, or technical documentation
   • Claim chart showing element-by-element infringement

4. Basis for Standing

   • Who owns the patent and has right to enforce
   • If licensee, evidence of exclusive licensing arrangement

5. Demands

   • What the patent holder seeks: cessation of infringement, damages, licensing, undertaking not to infringe
   • Clarity about what would resolve the dispute

6. Response Deadline

   • Specific timeframe for response (typically 14-21 days)
   • Statement of intention to issue proceedings if no satisfactory response

7. Costs Warning

   • Notification that if proceedings are issued, the recipient may be liable for legal costs
   • Reference to IPEC cost caps or Patents Court cost exposure as appropriate

8. ADR Statement

   • Whether the patent holder is willing to engage in Alternative Dispute Resolution (mediation, expert determination)
   • This is a mandatory consideration under pre-action protocols26

Technical Evidence Requirements

The quality and specificity of technical evidence in an LBA significantly affects its credibility and the prospect of settlement.

Claim Chart Analysis

A claim chart is the foundational technical evidence for an infringement allegation. It maps each element of the asserted patent claims to specific features of the accused product or process.27

Under UK Civil Procedure Rules Part 63, when infringement proceedings are commenced, the statement of case must show which claims are alleged to be infringed and give at least one example of each type of infringement.27a In IPEC, the court may require parties to create "a suitable chart, diagram or other document stating which integers of the claim are embodied in the allegedly infringing product."[27b] This same level of specificity is expected—though not formally mandated—at the LBA stage to demonstrate a credible infringement allegation.

What a claim chart must demonstrate:

• Element-by-element correspondence: Every element (or "integer") in the independent claims must be shown in the accused implementation27c
• Literal infringement or doctrine of equivalents: Under the test established in Actavis v Eli Lilly 2017 UKSC 48, specify whether infringement is alleged under normal claim interpretation (literal) or the doctrine of equivalents (immaterial variants)27d
• Specificity: Vague assertions like "your product appears to use our method" are insufficient—cite specific features, code, system architecture, or process steps with traceable evidence27e

For software patents, where source code is typically unavailable at the pre-action stage, proving infringement presents unique challenges due to the intangible nature of software operating remotely in compiled code.27f Claim charts must rely on:

• Observable system behaviour (performance characteristics, outputs, and functionality)
• Public-facing documentation and specifications
• Reverse engineering results (where lawful under UK copyright law)27g
• Marketing materials and user guides describing functionality

Product/System Identification

The LBA must clearly identify what allegedly infringes.28 Under pre-action protocol guidance, the letter should include:

• Description of the allegedly infringing product with sufficient detail28a
• Product names and version numbers
• Specific features or modules within larger systems
• Processes or methods being practiced
• Evidence of the infringing activity, such as dates and means of discovery (website captures, purchase receipts, product samples)28b

Evidence Source

Explain how the patent holder knows about the infringement:28

• Purchased the accused product for analysis
• Reviewed public-facing technical specifications
• Observed system behaviour through lawful means
• Industry knowledge of how the technology works

We prepare LBA technical evidence by conducting detailed product analysis, building claim charts that map specific patent elements to identifiable product features, and documenting the technical foundation for infringement allegations. The strength of this technical evidence often determines whether settlement discussions begin productively or whether the recipient can dismiss the allegation as speculative.

Timeline: From LBA to Litigation

Understanding the timeline helps both senders and recipients plan their strategy.

Response Period

The typical response deadline stated in an LBA is 14-21 days, though this can vary based on case complexity.29 The recipient is expected to respond substantively within this period, though it's acceptable to request a reasonable extension if more time is needed to gather technical evidence.

Negotiation Period

After the initial response, parties are expected to engage in good faith to explore settlement.30 This may involve:

• Exchange of technical information and analysis
• Discussion of licensing terms
• Alternative Dispute Resolution (mediation or expert determination)
• Further investigation and evidence gathering

There is no fixed timeline for this phase—it depends on the parties' willingness to engage and the complexity of the technical and commercial issues.

Issuing Proceedings

If settlement negotiations fail, the patent holder may issue proceedings. However, the court expects a reasonable period of engagement before litigation.31 Filing immediately after the response deadline without genuine attempts at resolution can result in adverse costs findings.

Venue Selection

At this stage, the patent holder must decide whether to file in:

• IPEC: For smaller disputes (damages up to £500,000) with cost caps (£60,000 for liability determination)32
• Patents Court: For larger or more complex disputes with no cost or damages caps

This decision affects strategy, costs, and timelines significantly.

Responding to an LBA: Your Obligations and Options

Receiving an LBA creates both legal obligations and strategic choices.

You Must Respond

Ignoring an LBA is not advisable. Under pre-action protocols, failure to engage can result in:33

• Adverse costs orders if litigation proceeds
• Loss of opportunity to resolve the dispute pre-litigation
• Weakened position on procedural compliance arguments

Even if you believe the allegation is unfounded, acknowledge receipt and indicate you're evaluating the claim with legal and technical counsel.

What Your Response Should Include

A substantive response to an LBA typically addresses:34

1. Non-Infringement Position

   • Your own claim chart analysis showing why the patent claims are not met
   • Technical explanation of how your implementation differs from the claimed invention
   • Specific claim elements that are absent from your product/process

2. Invalidity Position

   • Prior art references that anticipate or render the patent obvious
   • Arguments regarding insufficient disclosure or added matter
   • Challenges to patent scope or interpretation

3. Request for Further Information

   • If the LBA is vague about which specific features allegedly infringe, request clarity
   • If the claim chart lacks specificity, request detailed technical analysis

4. ADR Willingness

   • State whether you're willing to engage in mediation or other ADR
   • This demonstrates good faith procedural compliance

Technical Evidence You Need

Responding effectively requires technical analysis as rigorous as the allegation itself:

Claim Chart Analysis: Review the patent holder's claim chart and prepare your own showing non-infringement. This requires detailed understanding of:

• How the patent claims should be properly construed
• What your actual implementation does (not what marketing materials suggest)
• Where genuine technical differences exist

Prior Art Research: If challenging validity, identify specific prior art references published before the patent's priority date that disclose the same invention. Academic papers, earlier patents, product documentation, and technical standards are common sources.

Product Specifications: Gather internal technical documentation, source code (if software), architecture diagrams, and development history to demonstrate what your implementation actually does.

Early Technical Expert Engagement is Critical

We typically engage with recipients immediately upon LBA receipt to:

• Assess whether the infringement allegations have technical merit
• Identify claim elements that are genuinely absent from the accused system
• Conduct prior art searches to support invalidity positions
• Prepare technical evidence that forms the foundation of a strong response

Responding without technical analysis risks either accepting unfounded allegations or dismissing legitimate claims without proper assessment.

Costs and Practical Considerations

Understanding the cost implications of LBAs helps inform strategic decisions.

Cost of Preparing an LBA

For patent holders, preparing a comprehensive LBA involves:

• Legal costs: Solicitor time for drafting and procedural compliance (typically £5,000-£15,000 depending on complexity)
• Technical expert costs: Claim chart preparation, product analysis, evidence documentation (£3,000-£10,000)
• Total: £8,000-£25,000 for a well-prepared LBA

Cost of Responding to an LBA

For recipients:

• Legal costs: Solicitor review and response drafting (£5,000-£15,000)
• Technical expert costs: Claim chart review, non-infringement analysis, prior art searching (£5,000-£15,000)
• Total: £10,000-£30,000 for a comprehensive response

Costs Consequences of Non-Compliance

The court has discretion to penalize parties who fail to comply with pre-action protocols.35 If a patent holder skips the LBA stage without justification and proceeds directly to litigation, the court may:

• Order the patent holder to pay the defendant's costs of responding to the claim
• Reduce the costs the patent holder can recover if successful
• Make other adverse costs orders reflecting the procedural breach

Similarly, if a recipient fails to engage meaningfully with an LBA and later concedes the claim, the court may impose enhanced costs penalties.

Alternative Dispute Resolution

ADR is a formal consideration under pre-action protocols.36 Common ADR options at the LBA stage include:

• Mediation: Facilitated negotiation with neutral mediator
• Expert determination: Technical expert assesses infringement/validity and parties agree to be bound by the determination
• Structured negotiation: Direct licensing discussions with defined timelines

ADR can resolve disputes faster and cheaper than litigation, and the court expects parties to consider it seriously before filing proceedings.

Conclusion: The Strategic Importance of the LBA Stage

The Letter Before Action is far more than a procedural formality—it's a critical strategic stage that sets the tone for the entire patent dispute.

Key Takeaways:

• The LBA is mandatory: Under UK Civil Procedure Rules, you cannot simply file patent proceedings without pre-action engagement
• Technical evidence is essential: Vague allegations or responses are ineffective—rigorous claim chart analysis and prior art research form the foundation of credible positions
• Unjustified threats create liability: Patent holders must carefully target LBAs to primary actors only, avoiding customers and retailers
• Good faith engagement matters: Courts penalize non-compliance with pre-action protocols through adverse costs orders
• Early resolution is possible: Many UK patent disputes settle at the LBA stage when supported by strong technical evidence

The UK procedural framework differs fundamentally from US practice—understanding these requirements is critical for international companies facing UK patent disputes for the first time.

We prepare technical evidence for both patent holders sending LBAs and recipients responding to them. Our claim chart analysis, prior art research, and product assessment provide the technical foundation for effective pre-litigation strategy. Getting this evidence right at the LBA stage often saves significant litigation costs later—or avoids litigation entirely.

If you're preparing or responding to a UK Letter Before Action and need technical analysis, we can help. Our First consultation is free—get in touch to discuss your situation.

---

This article focuses on England and Wales procedure under the Civil Procedure Rules. Scotland and Northern Ireland have different procedural requirements. This is general information about UK patent dispute procedure, not legal advice. Always consult UK-qualified solicitors for advice specific to your situation.

---

Sources

1. Practice Direction - Pre-Action Conduct and Protocols — UK Ministry of Justice official pre-action requirements
2. Letter of claim (patent infringement) - Practical Law — UK letter before action guidance
3. An International Guide to Patent Case Management for Judges - United Kingdom — WIPO guidance on UK pre-action requirements
4. Ashurst Quick Guide - Pre-action Conduct in the English Courts — Purpose and requirements of pre-action protocols
5. Part 63 – Intellectual Property Claims - CPR — Official civil procedure rules for IP claims
6. Practice Direction 63A – Intellectual Property Claims — Supplementary guidance for IP claims procedures
7. Practice Direction – Pre-Action Conduct and Protocols — General pre-action conduct requirements
8. Walking the Tightrope of Cease-and-Desist Letters - Finnegan — US cease and desist strategic considerations and differences from UK approach
9. Cease and desist letters for IP infringement in the UK - Virtuoso Legal — UK vs international approach to pre-litigation letters
10. Patent infringement action—flowchart - LexisNexis — UK patent litigation procedure flowchart showing LBA stage
11. WIPO Patent Case Management Guide - UK Pre-Action — Response deadlines and timelines
12. WIPO Patent Case Management Guide - UK Pre-Action — Exceptions to letter before action requirement
13. Practice Direction – Pre-Action Conduct and Protocols — Court's consideration of pre-action protocol compliance for costs orders
14. Non-compliance with pre-action provisions - LexisNexis — Sanctions and costs consequences for pre-action protocol breaches
15. Part 44 – General Rules About Costs - CPR — Court's discretion on costs orders and factors considered
16. Patents Act 1977 - Section 70 — UK statutory basis for unjustified threats regime
17. Manual of Patent Practice - Section 70A — Definition of what constitutes a threat of infringement proceedings 17a. FH Brundle v Perry [2014] EWHC 475 (IPEC) — Case law establishing that the "reasonable person" test is objective and the sender's intention is irrelevant
18. Patents Act 1977 - Section 70A — Statutory provision on actionable threats and distinction between primary and secondary acts
19. WIPO Patent Case Management Guide - UK Actionable Threats — Who can be contacted without creating unjustified threats
20. Patents Act 1977 - Section 70A(2) — Statutory definition of primary acts (making/importing products; using processes) that are not actionable when threatened
21. The Patents Act 1977 (as amended) - Section 70A — UK IPO guidance on threats against secondary infringers 21a. Shenzhen Carku Technology Ltd v The NOCO Company [2022] EWHC 2034 (Pat) — Modern case law establishing that threats to online retailers/marketplaces regarding secondary acts constitute actionable unjustified threats
22. Manual of Patent Practice - Section 70B — Rationale for primary/secondary actor distinction and permitted communications
23. Manual of Patent Practice - Section 70C — Defence for inability to locate primary actor
24. The Patents Act 1977 (as amended) - Section 70C — Remedies for unjustified threats
25. Letter of claim—patent infringement - LexisNexis — Required contents of UK patent infringement letter
26. Practice Direction - Pre-Action Conduct and Protocols — ADR requirement in pre-action protocols
27. Claim Chart - IIPRD — Claim chart methodology and requirements 27a. CPR Part 63 and Practice Direction 63A Para 4.1 — Requirement that statement of case must show which claims are infringed and give at least one example of each type of infringement 27b. WIPO Patent Case Management Guide - UK Case Management — IPEC may require charts/diagrams showing which integers of the claim are embodied in the allegedly infringing product 27c. Practice Direction 63A Para 4.1 — Element-by-element (integer-by-integer) correspondence requirement in UK patent infringement pleadings 27d. Actavis UK Ltd v Eli Lilly [2017] UKSC 48 — Supreme Court establishes two-limb test for patent infringement: normal interpretation (literal) vs doctrine of equivalents (immaterial variants) 27e. Demystifying Patent Infringement: Evidence Of Use Charts - Mondaq — Specificity requirements for claim charts including traceable evidence from product documentation and technical specifications 27f. Enforcing software patents: seizing the moment - Carpmaels & Ransford — Challenges of proving software patent infringement due to intangible nature and unavailability of source code 27g. IBM United Kingdom Ltd v LzLabs GmbH [2025] EWHC 532 (TCC) — UK law on lawful reverse engineering for interoperability, observation, and analysis
28. Letter of claim—patent infringement - LexisNexis — Evidence requirements for LBA 28a. How to draft a letter of claim in an IP dispute - LexisNexis — Requirement for description of allegedly infringing product with sufficient detail 28b. Letter of claim—patent infringement - LexisNexis — Evidence of infringing activity including dates and means of discovery
29. WIPO Patent Case Management Guide - UK Pre-Action — Response deadlines in UK patent disputes
30. Ashurst Quick Guide - Pre-action Conduct — Good faith engagement obligations
31. WIPO Patent Case Management Guide - UK Pre-Action — Timeline to proceedings after LBA
32. IPEC Guide — IPEC cost caps and damages limits
33. WIPO Patent Case Management Guide - UK Pre-Action — Costs consequences of non-compliance
34. Defence and counterclaim—patent infringement claim - LexisNexis — Response options for patent infringement allegations
35. Practice Direction - Pre-Action Conduct and Protocols — Court's discretion to impose costs penalties
36. Practice Direction - Pre-Action Conduct and Protocols — ADR requirements under pre-action protocols