Managing Willfulness Risk After a Patent Notice Letter: A Practical Guide

Summary. This guide takes a company from the day a patent notice letter arrives to the point where it has a defensible record on willfulness, whether the matter ends in silence, a license, a redesign, an inter partes review, or a lawsuit. It opens with the decisions to make before acting, then sets out twelve steps: triage, routing to counsel and controlling internal communications, a litigation hold, assessing declaratory judgment risk, a privileged preliminary analysis, choosing between a formal opinion and informal advice, documenting a design-around, deciding on a Patent Office challenge, writing the response letter, managing customers and suppliers, tendering to insurers, and monitoring. Each step explains what to do, why, the governing authority, common pitfalls, timing, and typical cost ranges. A separate part covers the patent owner who is drafting the letter. A timeline and cost table, an extended worked example involving a lighting manufacturer and a patent assertion entity, common mistakes, an FAQ, and practical takeaways close the guide.

The envelope arrives at the front desk of Lumenfold Lighting, a 60-person maker of commercial LED fixtures, on a Tuesday. Inside is a four-page letter from a company called Brightwater IP Holdings LLC. It identifies two patents on dimming-driver circuits, names Lumenfold's best-selling Arc series by model number, attaches a claim chart for one claim of each patent, and "invites" Lumenfold to discuss a license within 21 days. The receptionist scans it to the chief executive, who forwards it to the head of engineering with one line: "Is this real?"

The engineer's answer, whatever it is, will probably be the first document in the willfulness file. In patent law, the period after a notice letter is when an accused infringer's state of mind is formed and recorded. What the company investigates, concludes, writes down, and changes in the following weeks will shape whether a jury later finds willful infringement and whether a judge multiplies the damages, potentially to three times the compensatory award under 35 U.S.C. § 284.

This guide walks through that period step by step. It is written mainly for the recipient, but it includes a section for the patent owner, because the same rules determine how a letter should be drafted.

The short answer

• Do not ignore it, and do not answer it yet. Route the letter to counsel the same day, preserve documents, and stop informal commentary. Respond within a deliberate timetable, not the letter's.
• Knowledge is now established. A letter naming a patent and a product usually supplies the knowledge that is a "prerequisite to enhanced damages," WBIP, LLC v. Kohler Co., 829 F.3d 1317 (Fed. Cir. 2016). From here on, the question is whether the company's conduct is deliberate infringement or good-faith business.
• You do not have to buy an opinion. 35 U.S.C. § 298 bars using the failure to obtain or present advice of counsel to prove willfulness or intent to induce. But you do need a reasoned, contemporaneous basis for continuing, and you need to be able to show good faith without necessarily waiving privilege.
• The letter may let you sue first. Under MedImmune, Inc. v. Genentech, Inc., 549 U.S. 118 (2007), and SanDisk Corp. v. STMicroelectronics, Inc., 480 F.3d 1372 (Fed. Cir. 2007), a specific assertion of rights against identified products generally creates declaratory judgment jurisdiction. That is an option and a risk.
• Build visible evidence of good faith. A design-around record, an engineering change order, a decision memo, or a timely petition for inter partes review are all evidence a jury can see without the company waiving privilege over legal advice.
• Budget realistically. A disciplined response without litigation commonly costs from the low five figures (triage, privileged review, a response letter) to the low six figures (formal opinions on several patents or an IPR petition). Litigation through trial costs far more.

Before you start: five decisions

1. Who sent it, and what do they want? An operating competitor usually wants you out of the market or paying a royalty that protects its margins; it may seek an injunction under 35 U.S.C. § 283. A patent assertion entity usually wants a license fee and is often sending similar letters to many companies. A university or individual inventor may want recognition and a license. The sender's identity affects tone, settlement value, and whether litigation is likely.

2. Is this a notice letter, an offer, or a threat? Letters range from a bare "we own these patents and you may want a license" to a draft complaint. A letter that identifies specific patents and specific products is the kind that supplies knowledge, may start the damages clock under 35 U.S.C. § 287(a), and may create declaratory judgment jurisdiction.

3. What is at stake commercially? Estimate the revenue from the accused products over the past six years (the damages window under 35 U.S.C. § 286) and the next three to five years. A product line approaching end of life calls for a different strategy than a flagship.

4. Who must be involved? In most companies: the general counsel or outside counsel, one senior technical lead, the business owner of the product line, and finance. Keep the group small and documented.

5. Who is the right outside counsel, and for which job? The lawyers who provide an opinion you might rely on should ordinarily not be the lawyers who would try the case. Decide early who will do privileged triage, who might write a formal opinion, and who would litigate.

Step 1: Triage the letter within 48 hours

What to do. Log the date and manner of receipt and who has seen it. Pull each patent and confirm basic facts: issue date, expiration date (generally 20 years from the earliest nonprovisional filing date under 35 U.S.C. § 154, subject to adjustments), maintenance fee status, the recorded owner in the USPTO assignment database (see 35 U.S.C. § 261), pending continuations, prior litigation, and any prior IPR or reexamination. Identify the accused products and their sales, and note any deadline in the letter.

Why. Many letters fall apart at triage. A patent may be expired, lapsed for nonpayment, owned by someone other than the sender, or already narrowed by the Patent Office. Conversely, a pending continuation is a warning that the patentee may draft new claims aimed at your product.

Authority and pitfalls. If the patent owner sells products, check whether those products are marked; unmarked sales limit the owner's damages to the period after actual notice, and actual notice "requires the affirmative communication of a specific charge of infringement by a specific accused product or device," Amsted Industries Inc. v. Buckeye Steel Castings Co., 24 F.3d 178 (Fed. Cir. 1994). The notice must also come from the patentee, Lans v. Digital Equipment Corp., 252 F.3d 1320 (Fed. Cir. 2001). The most common pitfall at this step is sending the letter around the company for comment.

Timing and cost. One to two days. Internal time, or a few hours of outside counsel.

Step 2: Route to counsel and control internal communications

What to do. Have counsel issue a short written instruction to everyone who has seen the letter: do not discuss the patents or the letter in email, chat, or meetings except at counsel's request; send questions to counsel; do not forward the letter. Set up a privileged channel (a dedicated, labeled email thread or matter folder) for any analysis. When engineers provide technical input, have counsel request it in writing, so the work is done to help counsel give legal advice.

Why. Willfulness is about state of mind, and the best evidence of state of mind is what employees wrote at the time. Casual messages like "we probably infringe but they will never sue" or "legal says ignore it" are not privileged and often decide the willfulness verdict. Communications made to obtain legal advice, by employees at counsel's request, can be privileged under Upjohn Co. v. United States, 449 U.S. 383 (1981), and analysis prepared in anticipation of litigation can be protected work product under Fed. R. Civ. P. 26(b)(3) and Hickman v. Taylor, 329 U.S. 495 (1947).

Pitfalls. Labeling something "privileged" does not make it so. Business discussions about pricing or launch timing that happen to copy a lawyer are generally not privileged. Do not instruct employees to avoid learning about the patent; a policy designed to avoid knowledge can look like willful blindness under Global-Tech Appliances, Inc. v. SEB S.A., 563 U.S. 754 (2011). The goal is to channel knowledge to counsel, not to suppress it. For the corporate privilege rules in more depth, see Attorney-Client Privilege and Work Product for Businesses: Upjohn, In-House Counsel, and the Common Interest.

Timing and cost. Same day. Minimal cost.

Step 3: Issue a litigation hold

What to do. Decide whether litigation is reasonably anticipated. For a specific letter naming products, the answer is usually yes. Issue a written hold to custodians in engineering, product management, sales, and leadership, covering design files, source code repositories, engineering change orders, test data, product specifications, sales and pricing data for the accused products, communications about the patentee, and any prior freedom-to-operate work. Suspend auto-deletion for those custodians and systems. Track acknowledgments.

Why. The duty to preserve arises when litigation is reasonably anticipated, and a failure to preserve electronically stored information can lead to sanctions under Fed. R. Civ. P. 37(e), including adverse-inference instructions where a party acted with intent to deprive. A willfulness defense depends on the same records a hold preserves: the dates of design changes and the evidence of good-faith investigation.

Pitfalls. Holds that are too broad are ignored; holds that are too narrow miss the chat platform where engineers actually talk. Remember that a hold notice itself is usually privileged, but the fact and date of the hold may be discoverable. For a full checklist, see Litigation Hold and Evidence Preservation Checklist: A Practical Checklist, and for the sanctions law, Litigation Holds, Spoliation, and Rule 37(e): Preserving Electronic Evidence Before It Costs You the Case.

Timing and cost. Within a week. Low four figures for counsel time in a small company; more where systems are complex.

Step 4: Assess declaratory judgment risk and opportunity

What to do. Ask counsel two questions. First, does the letter give the company the right to file a declaratory judgment action of noninfringement or invalidity now, under 28 U.S.C. § 2201? Second, would anything the company says in response create or strengthen that right, or alternatively invite the patentee to sue first?

Why. MedImmune rejected the old "reasonable apprehension of suit" test in favor of an all-the-circumstances inquiry into whether there is "a substantial controversy, between parties having adverse legal interests, of sufficient immediacy and reality." The Federal Circuit applied it in SanDisk: where a patentee asserts rights under a patent based on identified ongoing or planned activity, and the other party contends it has the right to engage in that activity without a license, there is a case or controversy. Letters that carefully avoid threatening suit can still suffice. In Hewlett-Packard Co. v. Acceleron LLC, 587 F.3d 1358 (Fed. Cir. 2009), a patent holding company's letter identifying a patent and a product line, imposing a response deadline, and asking that the recipient not file suit supported jurisdiction. In 3M Co. v. Avery Dennison Corp., 673 F.3d 1372 (Fed. Cir. 2012), communications suggesting that specific products may infringe and offering a license were enough.

The strategic choice. Filing first lets the recipient choose the forum and timing, and a declaratory judgment plaintiff is not limited by the patent venue statute that would govern a suit against it, 28 U.S.C. § 1400(b), as construed in TC Heartland LLC v. Kraft Foods Group Brands LLC, 581 U.S. 258 (2017); declaratory judgment venue generally follows 28 U.S.C. § 1391, subject to personal jurisdiction over the patentee. But filing first escalates a dispute that might have ended with a letter, and courts have discretion to decline jurisdiction or transfer.

A trap for IPR planning. If the company files a civil action challenging the validity of a claim before it files an IPR petition, the IPR is barred, 35 U.S.C. § 315(a)(1). A counterclaim of invalidity in a suit the patentee filed does not trigger that bar. A company that may want an IPR should file a noninfringement-only declaratory judgment complaint, or file the petition first.

Timing and cost. The analysis takes a few days. Filing a declaratory judgment complaint is a litigation decision with litigation costs. For the procedure, see Filing or Defending a Declaratory Judgment Action: A Practical Guide.

Step 5: Commission a privileged preliminary analysis

What to do. Have counsel, with technical input requested by counsel, prepare a privileged preliminary assessment. It should cover: the claims most likely to be asserted (not only the ones charted); how disputed terms are likely to be construed; how the accused products actually work, from schematics and code rather than marketing material; a first look at invalidity under 35 U.S.C. § 102, § 103, and § 112, and eligibility under § 101 and Alice Corp. v. CLS Bank International, 573 U.S. 208 (2014) for software and business-method claims; a rough exposure estimate; and options (do nothing, respond, license, redesign, challenge).

Why. The assessment tells the company whether it needs a formal opinion, a design-around, a Patent Office challenge, or a license. It also creates a contemporaneous, privileged record that counsel considered the patent seriously, which may matter later even if it is never produced.

Authority and pitfalls. If the assessment might later be relied on, it must be thorough: an opinion that is conclusory or based on incomplete facts can hurt more than help, as in nCube Corp. v. SeaChange International, Inc., 436 F.3d 1317 (Fed. Cir. 2006), where the court affirmed enhancement after the defendant failed to give opinion counsel a key technical document. Give counsel the real product facts. Do not let the exposure estimate drift into emails with business teams. Remember that invalidity must be proved by clear and convincing evidence in court under 35 U.S.C. § 282 and Microsoft Corp. v. i4i Ltd. Partnership, 564 U.S. 91 (2011), but only by a preponderance in an IPR under 35 U.S.C. § 316(e). For infringement analysis method, see What Constitutes Patent Infringement: Claims and Defenses: A Practical Guide and How to Read a Patent: Claims, Specification, and Prosecution History.

Exposure arithmetic. Start with accused revenue in the six-year window, apply a plausible royalty range, and then consider limits: marking (no pre-notice damages if the patentee sold unmarked products), the patent's expiration, and apportionment to the patented feature. Then show the enhancement range separately, so leadership sees how much of the risk is driven by conduct from now on.

Timing and cost. Two to six weeks. Commonly from the high four figures to the mid five figures per patent, depending on complexity and prior-art searching.

Step 6: Choose between a formal opinion and informal advice

What to do. Based on the preliminary analysis, decide whether to commission a formal written opinion from outside patent counsel that the company may rely on, to keep advice informal and privileged, or both.

Why. No one is required to obtain an opinion, a rule established when the Federal Circuit overruled the old affirmative duty of care in In re Seagate Technology, LLC, 497 F.3d 1360 (Fed. Cir. 2007) (en banc), and later codified in part by § 298. And since Knorr-Bremse Systeme Fuer Nutzfahrzeuge GmbH v. Dana Corp., 383 F.3d 1337 (Fed. Cir. 2004) (en banc), no adverse inference may be drawn from keeping advice privileged. Even so, after Halo Electronics, Inc. v. Pulse Electronics, Inc., 579 U.S. 93 (2016), culpability is measured by what the company knew and believed at the time it acted, and a timely, competent opinion remains the most direct evidence that the company believed in good faith that it did not infringe or that the patent was invalid. It speaks to the second of the factors in Read Corp. v. Portec, Inc., 970 F.2d 816 (Fed. Cir. 1992) and to the jury's question whether infringement was deliberate.

When a formal opinion is usually worth it. The stakes are high (a flagship product, a competitor seeking an injunction); the defense is strong and explainable; the company is prepared to waive privilege over the opinion's subject matter; and the opinion can be obtained promptly. When the stakes are modest, or the analysis is close and the company would not want to show it to a jury, privileged informal advice often makes more sense.

What a reliable opinion contains. Written by qualified patent counsel; addresses each potentially asserted claim; construes disputed terms using the specification and prosecution history; compares the claims to the accused product as actually built (from documents, not descriptions); addresses literal infringement and the doctrine of equivalents; for invalidity, identifies specific prior art and applies the clear-and-convincing standard; states its assumptions and the materials reviewed; and is updated if the product or the claims change. Courts have long asked whether an opinion was thorough enough to "instill a belief in the infringer that a court might reasonably hold the patent is invalid, not infringed, or unenforceable," Ortho Pharmaceutical Corp. v. Smith, 959 F.2d 936 (Fed. Cir. 1992).

The waiver. Relying on an opinion waives privilege over its subject matter. Under In re EchoStar Communications Corp., 448 F.3d 1294 (Fed. Cir. 2006), the waiver reaches communications with any counsel, in-house or outside, about the same subject, and documents reflecting those communications, but generally not counsel's internal work product that was never communicated to the client. Seagate held that reliance on opinion counsel generally does not waive privilege over trial counsel's communications. The general rule on subject-matter waiver is Fed. R. Evid. 502(a). Keep opinion counsel and trial counsel separate, and assume that everything the company sent to opinion counsel may be read by the patentee.

Pitfalls. Opinions obtained only after suit say little about pre-suit good faith. Opinions written to the conclusion the client wanted, on facts the client curated, can backfire; in Arctic Cat Inc. v. Bombardier Recreational Products Inc., 876 F.3d 1350 (Fed. Cir. 2017), the Federal Circuit affirmed willfulness and trebled damages where the defendant waited years before seeking competent advice. An opinion on invalidity alone does not defeat inducement, because a good-faith belief of invalidity is no defense to inducement under Commil USA, LLC v. Cisco Systems, Inc., 575 U.S. 632 (2015).

Timing and cost. Three to eight weeks. Formal opinions commonly cost in the mid five figures per patent and can exceed six figures for complex validity work across several patents. Engagement terms that define scope, assumptions, and independence are in the Willfulness Toolkit: Notice Letter Responses, Opinion of Counsel Engagements, and Read Factor Analyses.

Step 7: Design around, and document it

What to do. If the analysis shows meaningful risk, ask engineering whether the product can be changed to avoid the claims without unacceptable cost or performance loss. Have counsel identify the claim limitations to avoid. Have engineering propose alternatives. Have counsel review the chosen alternative before release. Record the work in ordinary business documents: an engineering change order or design review record that states the change, the date, the products affected, and that the change was made "to reduce intellectual property risk," without describing the legal advice.

Why. Designing around patents is lawful and, in the Federal Circuit's words, one of the benefits of the patent system, State Industries, Inc. v. A.O. Smith Corp., 751 F.2d 1226 (Fed. Cir. 1985). A prompt, good-faith redesign is "remedial action" under the seventh Read factor, can end the period of any willful infringement, and is visible to a jury without waiving privilege. The reasoning of Westvaco Corp. v. International Paper Co., 991 F.2d 735 (Fed. Cir. 1993), which reversed an enhancement where the defendant had worked to design around the patent, still frames how courts see a genuine redesign effort.

Pitfalls. A redesign that is not colorably different, or that is launched only after suit, carries less weight. Engineers should not write that the old design "definitely infringes"; the record should describe the change, not concede liability. Consider whether the redesign itself could infringe a pending continuation. And decide what happens to existing inventory, because continuing to sell old-design units after a redesign is ready can look deliberate.

Timing and cost. Weeks to months, depending on the product. Cost is mostly engineering time; counsel review of the redesign is commonly in the four to low five figures.

Step 8: Decide whether to challenge the patent at the Patent Office

What to do. Evaluate an inter partes review under 35 U.S.C. § 311, a post-grant review if the patent is within nine months of issuance under 35 U.S.C. § 321, or an ex parte reexamination request under 35 U.S.C. § 302. Consider timing, the strength of the printed prior art, estoppel, and cost.

Why. A well-founded petition, filed promptly, documents a contemporaneous belief in invalidity, may lead to cancellation of the claims, and can prompt the patentee to settle. The burden in an IPR is a preponderance of the evidence, lower than in court.

Authority and pitfalls.

• IPR is limited to anticipation and obviousness based on patents and printed publications, 35 U.S.C. § 311(b).
• The petition must be filed within one year after service of a complaint alleging infringement, 35 U.S.C. § 315(b). Before suit, there is no statutory deadline, but delay weakens the willfulness value.
• A petitioner who obtains a final written decision is estopped from asserting in court any ground it raised or reasonably could have raised, § 315(e)(2).
• Institution is discretionary under 35 U.S.C. § 314(a). The USPTO's approach to discretionary denial, including how it weighs parallel litigation and the patent's age, changed significantly in 2025, when the USPTO rescinded its 2022 guidance on parallel litigation and moved discretionary-denial decisions to the Director level. Check the current Director guidance before advising on the likelihood of institution.
• Procedures are in 37 C.F.R. Part 42.
• Whether a jury will hear about the IPR is uncertain; many courts exclude non-final PTAB proceedings under Fed. R. Evid. 403. The judge deciding enhancement can consider it.

Timing and cost. Preparing a petition typically takes one to three months. Through a final written decision, IPRs commonly cost several hundred thousand dollars including USPTO fees, which are set under 35 U.S.C. § 41 and were adjusted in a fee rule effective January 19, 2025; check the current fee schedule before filing. Ex parte reexamination is cheaper but gives the requester no role after the request. For the process, see Filing or Defending an Inter Partes Review: A Practical Guide and Inter Partes Review Strategy: Discretionary Denial, Estoppel, and the Parallel District Court Case.

Step 9: Write the response letter

What to do. Choose among four responses:

Why. A measured response shows the company took the letter seriously, buys time, and can surface weaknesses in the sender's position. A standstill or tolling agreement can suspend the race to the courthouse while the parties talk. If the parties negotiate, ask for a nondisclosure agreement that covers the discussions.

Pitfalls. Do not admit infringement, describe your product in ways that track the claim language, or promise changes you have not decided on. Do not say you have "obtained an opinion" unless you are prepared to rely on it, because disclosing the conclusion of legal advice can support a waiver argument. Keep the letter factual and short. A response asserting that the company has the right to continue without a license confirms the adverse positions that SanDisk describes, which strengthens declaratory judgment jurisdiction; that may be what you want, but decide it deliberately. Templates are in the Willfulness Toolkit: Notice Letter Responses, Opinion of Counsel Engagements, and Read Factor Analyses, and broader advice on demand correspondence is in Drafting a Demand Letter: A Practical Checklist.

Bad-faith assertion laws. Many states have enacted statutes targeting bad-faith patent demand letters, often enforced by the state attorney general, and the Federal Trade Commission has treated deceptive demand-letter campaigns as unfair or deceptive practices under 15 U.S.C. § 45. If the letter is vague, threatening, or part of a mass campaign against small businesses, ask counsel whether a state statute applies. Because federal patent law preempts state liability for good-faith enforcement, these statutes reach only bad-faith assertions, and their coverage varies, so read the statute of the recipient's state.

Timing and cost. Send the first response within the letter's deadline or shortly after, even if only to acknowledge receipt and ask for information. Low four figures.

Step 10: Manage customers, suppliers, and indemnities

What to do. Determine whether the patentee has written, or is likely to write, to your customers or distributors. Review customer contracts for indemnity obligations and supplier contracts for indemnity rights. Notify suppliers whose components are implicated and tender defense where the contract allows. Coordinate communications with customers through counsel.

Why. Customer letters create inducement risk. Once you know of the patent and continue to supply customers with instructions on how to use the product, the patentee may allege induced infringement under 35 U.S.C. § 271(b), which requires knowledge of the patent and of infringement under Global-Tech, and actual intent to cause the infringing acts, Hewlett-Packard Co. v. Bausch & Lomb Inc., 909 F.2d 1464 (Fed. Cir. 1990). Section 298 protects you from proof of intent based on the absence of an opinion, but documentation and support materials can be evidence of intent. Commercially, customers will expect you to stand behind the product, and the Uniform Commercial Code's warranty against infringement in § 2-312(3), which applies to merchants regularly dealing in goods of the kind unless otherwise agreed, may impose obligations even without a contract clause.

Pitfalls. Do not tell customers "there is no problem" without a basis. Communications with customers and suppliers about a shared legal threat may be protected by a common-interest arrangement, but only if structured carefully; put it in writing before sharing analysis. For contract allocation, see Indemnification and Limitation of Liability: The Risk Allocation Engine of Every Contract, and for inducement, Pleading and Proving Induced and Contributory Patent Infringement: A Practical Guide.

Timing and cost. Start within two weeks. Cost depends on the number of contracts.

Step 11: Tender to insurers

What to do. Identify every policy that might respond: commercial general liability, any intellectual property infringement defense policy, errors and omissions or technology policies, and directors and officers coverage if executives are named. Give written notice promptly, as policies require, and keep a record.

Why. Coverage for patent infringement is limited. Standard commercial general liability forms generally exclude intellectual property infringement, with narrow exceptions in the "advertising injury" coverage that rarely reach patents. Specialized IP defense or infringement-abatement policies exist, but they usually exclude known claims, so a policy bought after the letter will not cover it. Late notice can forfeit coverage that does exist. Read the policies, not the summary.

Pitfalls. Do not assume no coverage without reading the policy. Do not assume coverage for enhanced damages: many policies and some state public-policy rules exclude punitive or multiplied damages. For coverage disputes, see Business Insurance and Coverage Disputes: CGL, E&O, Cyber, and D&O.

Timing and cost. Within the notice period of each policy, often "as soon as practicable." Minimal.

Step 12: Monitor, update, and prepare for the lawsuit

What to do. Calendar follow-ups: watch the patent family for continuations and new claims; re-run the analysis when the product changes; track the patentee's other suits and IPRs; and revisit the decision whether to obtain a formal opinion if the risk increases. If the patentee sues, the willfulness record you built becomes evidence, and several new decisions arise.

If you are sued.

• Pleading. Willfulness must be plausibly pleaded under Fed. R. Civ. P. 8 and Ashcroft v. Iqbal, 556 U.S. 662 (2009). A motion under Fed. R. Civ. P. 12(b)(6) may succeed where the complaint pleads knowledge only in conclusory terms. Courts disagree on whether knowledge from the complaint itself supports a claim for post-suit willfulness; see ZapFraud, Inc. v. Barracuda Networks, Inc., 528 F. Supp. 3d 247 (D. Del. 2021).
• Advice-of-counsel election. Expect a scheduling order deadline to elect whether you will rely on advice of counsel, under Fed. R. Civ. P. 16. Decide with the waiver scope in mind.
• Bifurcation. Consider asking to try willfulness separately under Fed. R. Civ. P. 42(b), or to defer willfulness discovery.
• The IPR clock. The one-year bar in § 315(b) runs from service of the complaint.
• Motions in limine. Move to exclude argument that the absence of an opinion shows willfulness. See Drafting and Opposing Motions in Limine: A Practical Guide.

The doctrine behind each of these decisions is explained in Willful Patent Infringement and Enhanced Damages After Halo: Knowledge, Opinions of Counsel, and Section 298.

If you are the patent owner sending the letter

The same rules tell a patent owner how to write a letter that does its job.

1. Decide what the letter is for. Starting § 287 damages, establishing knowledge for willfulness, opening license talks, or all three. Each requires specificity.
2. Be specific. Identify the patent, at least one claim, and the accused product by name or model. Attach a claim chart if you want the letter to support willfulness. Amsted requires "a specific charge of infringement by a specific accused product."
3. Send it from the right party. The patent owner or its authorized agent, per Lans. Confirm the recorded chain of title first; see Patent Ownership, Assignments, and Standing: Chain-of-Title Problems That Sink Cases.
4. Weigh declaratory judgment risk. A specific letter likely creates jurisdiction for the recipient to sue first in its home forum. If forum matters, be ready to file.
5. Mark your own products. Marking under § 287(a) preserves damages from the start and makes the letter less important for damages. See Patent Marking Compliance: A Practical Checklist.
6. Comply with bad-faith demand statutes. State laws may require specific content and penalize misleading assertions. Do not overstate litigation history or threaten suit you do not intend.
7. Preserve your own documents. The patentee's duty to preserve can arise when it decides to assert the patent.
8. Keep the record. Proof of delivery and of the recipient's receipt becomes evidence of knowledge.

For the broader question of when and how to enforce, see Do You Have to Enforce Your Patent? Duty, Demand Letters, and the Cost of Doing Nothing.

Timeline and cost overview

The ranges below are typical for a small or mid-sized company and one to three patents; they are estimates, not quotes, and vary by market and complexity.

Worked example: Lumenfold Lighting and the Brightwater letter

The facts are invented and simplified.

Day 0. Brightwater IP Holdings' letter arrives, identifying U.S. Patent Nos. 9,8XX,XXX and 10,1XX,XXX (dimming-driver circuits), claim 1 of each, and the Arc 200 and Arc 400 fixtures, with claim charts and a 21-day deadline to discuss a license. The chief executive forwards it to the engineering head, Dana Whitcombe, with "Is this real?"

Day 1 (Steps 1 and 2). Lumenfold's outside general counsel, Marcus Ilunga, asks the chief executive and Whitcombe not to reply to each other's emails on the subject and sends a short instruction to the four people who have seen the letter. He asks Whitcombe, in writing and for the purpose of giving legal advice, for the Arc driver schematics and firmware notes. Triage shows that the first patent expires in 14 months; the second has eight years left and a pending continuation. Brightwater does not make products, so marking is not an issue, and the six-year damages window reaches back to the Arc 200 launch. Brightwater has filed more than a dozen suits on the same family, most of which settled early.

Day 4 (Step 3). Ilunga issues a hold to seven custodians and the engineering wiki, and suspends chat auto-deletion for the hardware team.

Day 6 (Step 4). Ilunga advises that the letter likely gives Lumenfold declaratory judgment standing under SanDisk and Hewlett-Packard v. Acceleron. The leadership team decides not to file first: Brightwater's pattern suggests a business negotiation, and a lawsuit would cost more than a likely license. Ilunga notes that if Lumenfold later wants an IPR, it must not file an invalidity declaratory judgment action first, because of § 315(a)(1).

Day 14 (Steps 9 and 11). Lumenfold sends a two-paragraph acknowledgment: it has received the letter, takes intellectual property seriously, is reviewing the patents, and asks Brightwater to identify all claims it contends are infringed, the basis for any contention that the Arc 400 (which uses a different driver chip) infringes, and its licensing terms and licensing history. It makes no statements about its products. The same week, Lumenfold notifies its general liability carrier and its broker; the carrier reserves rights and cites the policy's intellectual property exclusion.

Weeks 2 to 6 (Step 5). Patent counsel retained by Ilunga reviews the schematics and the patents. Her privileged assessment: the Arc 200 likely meets claim 1 of the first patent; the Arc 400 likely does not meet either claim because its driver regulates current digitally rather than through the claimed analog feedback loop; the second patent's claim 1 is vulnerable to obviousness over two prior-art application notes from chip vendors. Exposure on the first patent is modest, given its remaining life and the Arc 200's declining sales.

Week 7 (Step 6). Lumenfold commissions a formal noninfringement and invalidity opinion on the second patent only, from a second firm, because that patent has eight years of life and covers the growth product. It decides not to obtain a formal opinion on the first patent.

Weeks 6 to 20 (Step 7). Engineering migrates the Arc 200 to the Arc 400's digital driver as part of a planned refresh, moving the refresh up by one quarter. The engineering change order states that the change was made "to consolidate driver platforms and reduce IP risk." Counsel reviews the final design against both patents and the pending continuation's published claims.

Week 10 (Step 9, continued). Brightwater responds with an offer of a portfolio license at a running royalty. Lumenfold counters with a paid-up offer limited to the first patent and to past Arc 200 sales, in a letter marked as a compromise communication, and asks for a short standstill.

Week 16. The formal opinion is delivered, concluding that the Arc 400 does not infringe the second patent and that claim 1 is likely invalid as obvious. Lumenfold keeps it in a separate file.

Week 22 (outcome). Brightwater accepts a paid-up license to the first patent covering past and remaining Arc 200 sales, and a covenant not to sue on the second patent for the Arc 400 as currently designed, for a single payment in the low six figures. If Brightwater had instead sued on the second patent, Lumenfold would have had a timely written opinion, a documented redesign, and a clean communications record to present on willfulness, plus a preserved IPR option within one year of service.

What made the difference. The chief executive's "Is this real?" email and Whitcombe's answer, which counsel asked him to send only to counsel, were the only informal messages about the letter. Everything else was either privileged or an ordinary business record that showed good faith.

Common mistakes

• Answering informally. The first internal reaction is often the most quoted document at trial.
• Ignoring a specific letter. Silence does not stop the clock, and continued sales after a specific charge are the most common foundation of a willfulness verdict.
• Letting engineers write legal conclusions. Ask for technical facts through counsel; keep conclusions with counsel.
• Buying an opinion too late. An opinion obtained after suit says little about pre-suit good faith.
• Shopping for a conclusion. Curating the facts given to opinion counsel turns a shield into evidence of bad faith.
• Filing an invalidity declaratory judgment action before an IPR. Section 315(a)(1) bars the petition.
• Talking about the advice. Telling customers or investors "our lawyers say we are fine" risks a waiver and may not be admissible to help you anyway.
• Forgetting customers. Continued supply with instructions after knowledge invites an inducement claim.
• Assuming insurance will pay, or assuming it will not. Read the policies and give notice.
• Redesigning without records. A design change that is not dated and documented is hard to prove.

Frequently asked questions

Is a letter that only "invites" a license discussion really a notice of infringement? It can be. For § 287 purposes, the question is whether it charges a specific product with infringement; a letter that names the product and encloses a claim chart usually does, as in Gart v. Logitech, Inc., 254 F.3d 1334 (Fed. Cir. 2001), where a letter identifying the patent and the product and suggesting a license was held sufficient. For willfulness, any letter that makes you aware of the patent supplies knowledge.

Can we sue for a declaratory judgment just because we are worried? Not without a sufficiently concrete dispute. Fear of a future suit, without an affirmative act by the patentee directed at your products, may not be enough, Prasco, LLC v. Medicis Pharmaceutical Corp., 537 F.3d 1329 (Fed. Cir. 2008).

Do we have to stop selling the product? No. Continuing to sell is lawful unless and until a court enjoins it. The question is whether you continue with a reasoned, good-faith basis.

Will the patentee see our privileged analysis? Only if you rely on it as a defense to willfulness, which waives privilege over its subject matter, or if privilege is lost through careless sharing.

Does an in-house lawyer's analysis count? It can support good faith, and it is privileged on the same terms as outside counsel's advice. EchoStar involved reliance on in-house counsel. For high-stakes matters, an independent outside opinion usually carries more weight with a jury.

Is an IPR a substitute for an opinion? They serve different purposes. An IPR documents an invalidity belief and may cancel claims; an opinion can also address noninfringement, which an IPR cannot.

What if the letter came from a competitor seeking an injunction? Move faster. Injunction risk makes a design-around or a declaratory judgment action more valuable, and the competitor's own marking and product sales affect the damages exposure.

What about a patent that has already expired? There is no injunction risk, but damages for the six years before suit remain possible, and a willfulness finding can still lead to enhancement of those damages.

Key takeaways

1. A specific letter establishes knowledge; your conduct afterward determines willfulness.
2. Route to counsel, preserve documents, and control internal communications on the first day.
3. Evaluate declaratory judgment jurisdiction both as a risk and as an option, and protect the IPR route.
4. Base continued sales on a privileged, fact-based analysis; commission a formal opinion when the stakes justify the waiver.
5. Make good faith visible in business records: design changes, decision memos, and timely Patent Office filings.
6. Answer the letter deliberately and without admissions, and manage customers, suppliers, and insurers in parallel.

The tasks in this guide are listed as check-off items in the Willfulness and Enhanced Damages Checklist: A Practical Checklist, and the letters, engagement terms, and worksheets are in the Willfulness Toolkit: Notice Letter Responses, Opinion of Counsel Engagements, and Read Factor Analyses.

This document is general information, not legal advice for any particular situation. Patent office practice, state demand-letter statutes, and district court rules change; confirm current requirements for a specific matter.

Related Documents

Related Articles

• Willful Patent Infringement and Enhanced Damages After Halo: Knowledge, Opinions of Counsel, and Section 298: the doctrine behind every step.
• Declaratory Judgment Actions: Jurisdiction, Discretion, and the Race to the Courthouse: when a letter lets you sue first.
• Inter Partes Review Strategy: Discretionary Denial, Estoppel, and the Parallel District Court Case: timing, estoppel, and institution risk.
• Attorney-Client Privilege and Work Product for Businesses: Upjohn, In-House Counsel, and the Common Interest: structuring privileged review.
• Do You Have to Enforce Your Patent? Duty, Demand Letters, and the Cost of Doing Nothing: the sender's perspective.
• Settlement Negotiation Tactics: Principled Negotiation, Anchoring, and Handling Hardball in Litigation: negotiating a license against a demand.

Related Guides

• Filing or Defending a Declaratory Judgment Action: A Practical Guide: the procedure if you decide to file first.
• Filing or Defending an Inter Partes Review: A Practical Guide: preparing and prosecuting a petition.
• Pleading and Proving Induced and Contributory Patent Infringement: A Practical Guide: customer-facing inducement risk.
• What Constitutes Patent Infringement: Claims and Defenses: A Practical Guide: the infringement analysis in your privileged review.
• Drafting and Opposing Motions in Limine: A Practical Guide: enforcing § 298 at trial.

Related Checklists

• Willfulness and Enhanced Damages Checklist: A Practical Checklist: every step as a check-off task.
• Litigation Hold and Evidence Preservation Checklist: A Practical Checklist: the hold you issue in Step 3.
• Freedom-to-Operate Search: A Practical Checklist: clearance work that prevents the next letter.
• Drafting a Demand Letter: A Practical Checklist: content and tone for pre-suit correspondence.

Related Toolkits

• Willfulness Toolkit: Notice Letter Responses, Opinion of Counsel Engagements, and Read Factor Analyses: response letters, engagement terms, and worksheets.
• Declaratory Relief Toolkit: Complaints, Jurisdictional Briefing, and Discretionary Dismissal: forms for a declaratory judgment action.
• PTAB Toolkit: Petitions, Patent Owner Responses, and Motions to Amend: IPR petition materials.
• Insurance Coverage Toolkit: Placing, Tendering, and Litigating Claims: tender letters and coverage analysis.