Sample Willful Infringement Demand Letters
Sample 1: Second Notice – Escalation to Willfulness Warning
[Law Firm / Patent Owner]
[Address]
[Email / Phone]
[Date]
VIA CERTIFIED MAIL, RETURN RECEIPT REQUESTED
AND EMAIL ([recipient email])
[Defendant Company]
[Address]
Attn: General Counsel / CEO
Re: SECOND NOTICE – Willful Infringement of U.S. Patent No. [X,XXX,XXX]
Dear [Recipient]:
This is our second letter regarding [Defendant]'s infringement of U.S. Patent No. [X,XXX,XXX] (the "'XXX Patent"), owned by [Patent Owner].
PRIOR NOTICE
By letter dated [First Letter Date], sent via certified mail (tracking number [XXXX]) and email, we notified [Defendant] that its [Product] infringes claims [1, 5, and 12] of the 'XXX Patent. We provided a detailed claim chart demonstrating infringement and demanded cessation.
That letter was delivered on [Delivery Date], as confirmed by [signed return receipt / email read receipt / delivery confirmation].
FAILURE TO RESPOND
It has now been [X] days since our letter was delivered. [Defendant] has not:
• Responded to our demand;
• Ceased manufacture or sale of the [Product];
• Contacted us to discuss resolution.
Despite actual knowledge of the 'XXX Patent and [Defendant]'s infringement, [Defendant] continues to sell the [Product]. We confirmed ongoing sales as recently as [Date] via [purchase / website screenshot / retailer listing].
WILLFUL INFRINGEMENT
[Defendant]'s continued infringement after receiving actual notice of the 'XXX Patent constitutes WILLFUL INFRINGEMENT under Halo Electronics, Inc. v. Pulse Electronics, Inc., 579 U.S. 93 (2016).
Willful infringement exposes [Defendant] to:
• ENHANCED DAMAGES up to THREE TIMES (3×) compensatory damages under 35 U.S.C. § 284
• ATTORNEY FEES as this is now an exceptional case under 35 U.S.C. § 285
• PERMANENT INJUNCTION against future infringement
Based on [Defendant]'s public sales data, we estimate [Defendant]'s current damages exposure at $[X]. With treble damages and attorney fees, total exposure could exceed $[3X + fees].
FINAL OPPORTUNITY
This is [Defendant]'s final opportunity to resolve this matter before litigation. Within ten (10) days of this letter, [Defendant] must:
1. Confirm in writing that all manufacture, sale, marketing, and distribution of [Product] has ceased;
2. Provide a complete accounting of [Product] sales (units, revenue, profit) since [Date of First Notice];
3. Propose adequate compensation for past infringement;
4. [Optional: Discuss licensing terms for future authorized sales].
If we do not receive a satisfactory response by [Deadline Date], [Patent Owner] will file a complaint for patent infringement in the United States District Court for the [District], seeking:
• Compensatory damages (lost profits or reasonable royalty)
• Enhanced damages for willful infringement
• Attorney fees
• Preliminary and permanent injunctive relief
• Costs
We will also consider ITC Section 337 proceedings to block importation of the [Product] if manufactured abroad.
[Defendant]'s refusal to engage in good faith after receiving clear notice of infringement will be presented to the court as evidence of willfulness.
Contact me immediately at [Phone/Email] to discuss resolution.
Very truly yours,
[Attorney Name]
[Firm Name]
Counsel for [Patent Owner]
Enclosures:
- Copy of First Demand Letter ([Date])
- Certified Mail Delivery Confirmation
- Evidence of Continued Sales (Screenshots dated [Date])
cc: [Patent Owner]
Sample 2: Final Pre-Litigation Demand
[Law Firm Letterhead]
[Date]
VIA FEDERAL EXPRESS OVERNIGHT AND EMAIL
[Defendant Company]
[Address]
Attn: Chief Executive Officer
General Counsel
Re: FINAL DEMAND – U.S. Patent No. [X,XXX,XXX] – Litigation Imminent
Dear [CEO Name] and Counsel:
NOTICE HISTORY
[Patent Owner] has twice notified [Defendant] of patent infringement:
• [Date 1]: Initial demand letter sent via certified mail and email, received [Date]
• [Date 2]: Second notice, willfulness warning, sent via certified mail and email, received [Date]
[Defendant] has not responded to either communication and continues to infringe.
WILLFUL INFRINGEMENT ESTABLISHED
The record now clearly establishes willful infringement:
1. KNOWLEDGE: [Defendant] received actual notice of the 'XXX Patent on [Date 1]
2. CONTINUED INFRINGEMENT: [Defendant] has sold [estimated units] of [Product] after notice
3. NO GOOD-FAITH BASIS: [Defendant] has not asserted any non-infringement or invalidity position
4. NO REMEDIAL ACTION: [Defendant] has not ceased sales, sought a license, or attempted design-around
Under Halo v. Pulse, this conduct is precisely the type of egregious, willful infringement that warrants enhanced damages.
DAMAGES EXPOSURE
Conservative Aggressive
Compensatory Damages: $[Amount] $[Amount]
Enhanced Damages (3×): $[3× Amount] $[3× Amount]
Estimated Attorney Fees: $[Amount] $[Amount]
----------- -----------
TOTAL EXPOSURE: $[Total] $[Total]
FINAL DEMAND
This is [Defendant]'s last opportunity to avoid federal litigation.
By 5:00 PM [Timezone] on [Date – 7 days], [Defendant] must:
□ Confirm cessation of all infringing activity
□ Provide sales accounting since [First Notice Date]
□ Make settlement offer of not less than $[Amount]
If these conditions are not met, [Patent Owner] will file suit in the [U.S. District Court] on [Date] without further notice.
All future correspondence should be directed to the undersigned. Direct contact with [Patent Owner] is not appropriate once litigation is imminent.
[Attorney Name]
[Firm]
[Contact]
cc: [Patent Owner] (via email)
Sample 3: Willfulness Demand – Deliberate Copyist
[Patent Owner]
[Address]
[Date]
[Defendant]
[Address]
Re: Deliberate Copying of Patented Technology – U.S. Patent No. [X,XXX,XXX]
Dear [Recipient]:
[Patent Owner] owns U.S. Patent No. [X,XXX,XXX] covering [technology description]. We have evidence that [Defendant] deliberately copied this patented technology.
EVIDENCE OF DELIBERATE COPYING
Our investigation reveals:
1. [Defendant]'s founder/CTO [Name] previously worked at [Patent Owner / Licensee] from [Dates] with access to the patented technology;
2. [Defendant]'s [Product] was launched [X] months after [Name] departed, implementing the same patented approach;
3. [Defendant]'s technical specifications and marketing materials use terminology identical to [Patent Owner]'s patent claims;
4. [Defendant]'s source code/design documents [if known from public sources] appear to implement the patented method.
This is not a case of independent development or innocent infringement. [Defendant] intentionally misappropriated [Patent Owner]'s patented innovation.
CONSEQUENCES OF DELIBERATE COPYING
Deliberate copying is the paradigm case of willful infringement. Under Halo v. Pulse, [Defendant]'s conduct warrants:
• Maximum enhanced damages (3× compensatory damages)
• Attorney fees as an exceptional case
• Potential trade secret claims if confidential information was also taken
• Possible personal liability for individuals involved in the copying
DEMAND
Given the deliberate nature of this infringement, [Patent Owner] demands:
1. Immediate cessation of all [Product] sales and development
2. Return or destruction of any materials derived from [Patent Owner]'s technology
3. Full accounting of development history and sales
4. [Compensation amount] settlement payment
5. Written acknowledgment of [Patent Owner]'s patent rights
[Defendant] has fourteen (14) days to respond. Given the evidence of deliberate copying, [Patent Owner] will pursue this matter aggressively if not resolved.
[Name]
[Title]
[Contact]
Sample 4: Response to Denial – Escalation
[Law Firm]
[Address]
[Date]
[Defendant's Counsel]
[Address]
Re: Response to Your [Date] Letter – U.S. Patent No. [X,XXX,XXX]
Dear Counsel:
We received your letter of [Date] denying infringement on behalf of [Defendant].
INADEQUATE RESPONSE
Your letter fails to provide any substantive basis for [Defendant]'s non-infringement position:
• No claim construction analysis
• No identification of which claim elements are allegedly missing
• No citation to prior art supporting invalidity
• No identification of any opinion of counsel
A conclusory denial is not a good-faith defense. [Defendant] cannot avoid willfulness by simply asserting "we don't infringe" without analysis.
OUR CLAIM CHART
We provided a detailed claim chart with our initial demand. Your response does not address any element of that chart. Unless [Defendant] can identify specific claim elements that its [Product] does not practice, infringement remains established.
WILLFULNESS IMPLICATIONS
[Defendant]'s choice to deny infringement without substantive analysis—while continuing to sell the [Product]—strengthens our willfulness case:
• [Defendant] has actual knowledge of the patent
• [Defendant] has not obtained an opinion of counsel (or will not produce one)
• [Defendant]'s denial is pretextual rather than good-faith
• [Defendant] continues to profit from infringement
This is precisely the type of "wanton" conduct that Halo identifies as warranting enhanced damages.
PATH FORWARD
We remain willing to discuss resolution. However, [Defendant] must:
1. Provide substantive non-infringement or invalidity analysis (claim-by-claim)
2. Cease sales pending resolution
3. Engage in good-faith settlement discussions
If [Defendant] simply continues selling while hiding behind a conclusory denial, we will file suit and seek maximum enhanced damages and fees.
Please respond with substantive analysis by [Date] or advise that [Defendant] is prepared for litigation.
[Attorney Name]