Patent Infringement Letter: All You Need To Know

calendar27 Apr, 2021
timeReading Time: 4 Minutes
Patent Infringement Letter

A patent infringement letter, aka a cease and desist letter, is sent to a person who is allegedly found guilty of infringing the intellectual property (IP) in question. Most patent owners prefer suing the alleged infringer instead of sending a pre-litigation letter. Inherently, the patent infringement letter may give an unfair advantage to the alleged infringer to sue the patentee in their desired jurisdiction.

But, sending a patent infringement letter has the advantage of setting up a date for losses to begin. This is not imperative if the concerned product is affixed with a patent number & date. Another option is filing suit in the first place rather than intimating the alleged infringer through a notification.

What is a Patent Infringement Letter?

Any concern shared by the patentee to an alleged infringer in written prior to filing a lawsuit can be deemed as a demand letter. However, a patent Infringement letter can be communicated for various legit reasons. Some examples include:-

  • An inquiry letter with a non-litigating intention to check whether a product covers the patent in question
  • An offer regarding licensing to initiate negotiations- this may lead to litigation if licensing conditions are not fulfilled.
  • A cease and desist letter asking for a royalty payment or discontinuation of using the patent
  • All these demand letters are imperative tools for patentee who seeks to safeguard their intellectual property. They lay a foundation for agreement rather than creating the chances of a lawsuit.

Read our article:Patent Term Extension in India: Affect & Criticism

Sending Demand Letter to Infringer under Bad Faith

Sending multiple patent letters to the concerned individual without any objective of filing a lawsuit is deemed detrimental. This is because neither do all letters’ recipients are familiar with patent law, nor do they have access to resources to challenge the petition in the court.

Consequently, they may agree to a settlement or pay a licensing fee even when the proposed allegation is far from reality. This practice, in a legal purview, known as sending a letter in bad faith, is highly vulnerable to potential legal actions.

Receiving a Patent Infringement Letter

If you receive a patent infringement letter from a party accusing you of patent violation, consult a patent attorney. Avoid overlooking such letters, as doing so can lead you to the zone of heavier penalties.

A response to such a letter should be crafted aptly, with consideration of the following factors:-

  • Whether the patentee has sued other entities previously for infringement?
  • Whether you have a business tie-up with a patent owner of any sort who sent the letter?
  • How successful, profitable, & popular the patent in pursuit is anticipated to be?
  • How stringent the infringement allegations are?
  • What sort of demands covered in the letter?

Reasons to Send a Patent Infringement Letter

Most of the courts perceive the practice of sending a patent infringement letter as a favorable one before filing a lawsuit. Although suing first allows you to pick apt jurisdiction, the jury may favor the infringer if you opt for a legal proceeding without attempting to negotiate. Below are some typical scenarios for when a person can send a patent infringement letter to an alleged infringer to protect the IPR rights.

  • Unauthorized replication of patented work for the sake of profit 
  • Alleged piece of work using technology that is violating patentee’s rights conferred by the Patent Act.
  • Invention offering something that is already provided by the prior invention by counterfeiting patented technology. 

What Information Should a Patent Infringement Letter Hold in General?

Although anyone can use a Patent infringement letter for various situations, such letters are generally used by individuals who seek to protect their work to conduct or make a living. In general, a Patent infringement letter should include:-

  • The receiver and sender’s name along with the contact details of the same. 
  • The date the letter was originally drafted. 
  • A clear and detailed description of the infringing activity. 
  • Timeline for allowing infringer to mend the loss before the sender leverages legal action.

This letter aims to prevent the alleged infringer from infringing the patented work; thus, it is advisable to avoid including any details that are irrelevant or not associated with the subject matter. 

Handling Different Patent Infringement Letters from Recipient’s Perspective

From intimating clients regarding the lawsuit to laying the ground for agreement, the patent infringement letter serves a different purpose. In general, such letters cater to three fundamental concerns given below, based on the intent of the letters, the recipient must act accordingly:-

Handling Different Patent Infringement Letters

License Negotiation

The letter may be an invitation to negotiate a license. For instance, if the patents come under a stand essential patent, they will need to follow a negotiation protocol under the appropriate antitrust laws. Also, the patentee might literally wish to avert litigation because of cultural revulsion, cost, and business[1] reasons. Comprehending the reasons why the patentee wishes to negotiate will help in any subsequent negotiation.

Pro Forma Negotiation

These letters are generally crafted in a friendly tone, but they can be equally deceptive as they may contain demands that are decorative and impractical. For example, the patentee may levy a tight deadline or ask for some actions that are detrimental to the Recipient. In totality, these letters favor the patentee because they can trick the Recipient into meeting the unreasonable demand and even swindling them to face unexpected legal proceedings.

Lawsuit Notice

Patent infringement letters may act as a notice of lawsuit for the accused. These letters are declarative and perhaps come with a compliant attached. These letters imply that the patentee is concerned about your stand regarding pre-emptive petition filing and wishes to have a case of their own in case the Recipient is tempted to leverage such action. The patentee might still want to negotiate aptly.


Genuinely, sending a patent infringement letter is an optimal way to avert costly litigation. The tone of the demand letter should not be abusive as it could incur stringent consequences for the sender. It’s better to draft such a letter under the guidance of the patent advocate so that your demands appear legitimate in front of the infringers. From a recipient’s point of view, such letters should be responded aptly after in-depth scrutiny. 

Read our article:What is the Culture for Working of Patent in India?

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