Received a Patent Infringement Letter? What to Check Before You Answer

What should you do after you receive a patent infringement letter?

Slow down and gather facts before anyone answers. A patent letter is an opening move, not a court order, and the most useful early work is quiet: reading, checking and saving records.

1. Note the basics. Write down the sender, the patent number or numbers, the product or feature accused, any deadline, and what the letter asks for (a license fee, a stop, or a meeting).
2. Keep everything. Tell the people who handle the accused product not to delete emails, design files, sales records or older versions of the code or product.
3. Check the patent itself. Confirm who owns it, whether it is still in force and when it expires, using the public USPTO records described below.
4. Read the claims, not the abstract. The numbered claims at the end of the patent define what it covers.
5. Look for insurance and indemnity. Some business policies and supplier contracts address intellectual property claims. Read the notice terms.
6. Hold your reply. Avoid phone calls or emails that describe how your product works or concede anything until you know what the patent covers.

If the letter came from a competitor about a trademark or copyright instead, the rules are different. Our guide to what to do after a cease and desist letter covers those.

Why do patent owners send letters before suing?

A letter can change how much money is at stake later. Under 35 U.S.C. section 287(a), a patent owner who sells a patented product without marking it with the patent number generally cannot recover damages until the accused infringer is notified. After that notice, damages can be recovered for infringement that continues. A detailed letter may be the sender's way of creating that notice.

Notice can also feed an argument about willfulness. Under section 284, a court may increase damages up to three times the amount found. Under section 285, a court may award attorney fees to the prevailing party, but only in exceptional cases.

How do you check whether the patent is valid, owned and still in force?

The first-round checks use free public records from the U.S. Patent and Trademark Office (USPTO). Each one can change the value of the claim against you.

An expired patent can still support a claim for past damages within the six-year window. It cannot stop future sales.

How can you tell if your product actually infringes the patent?

Infringement is measured claim by claim. A product generally infringes a claim only if it contains every element that claim describes. A letter that only names the patent and your product, without showing how each element is met, leaves the hardest question unanswered.

Example (hypothetical): a small online furniture store receives a letter saying its 'room preview' feature infringes a patent. Claim 1 requires five steps, including a 3D scan taken by the customer's phone. The store's tool uses flat product photos and no scanning. If that is accurate, the store can ask the sender to identify where the scan element appears, which the letter never addressed.

Asking for a claim chart (a table matching each claim element to a feature of your product) is a common, calm first request. Building one takes real work, so the reply shows how closely the sender studied your product.

What if the letter looks like a bad-faith patent shakedown?

Some patent letters are sent in bulk with little investigation. In 2014 the Federal Trade Commission settled charges against MPHJ Technology Investments, which the FTC said sent thousands of letters to small businesses claiming many companies had already paid for licenses, and law firm letters threatening suits within two weeks that were never filed. The settlement barred the company and its lawyers from false or unsupported claims about how widely the patents had been licensed, and from misrepresenting that a lawsuit was coming.

• The letter names no specific claim or product feature.
• It cites other companies that supposedly paid, with no names or numbers you can check.
• It sets a very short deadline and a fee that looks priced to be cheaper than a lawyer.
• The sender is a company you cannot connect to the patent's recorded owner.

Several states have passed laws aimed at bad-faith patent demand letters. Which state laws, if any, reach a particular sender is a question for a lawyer, because patent rights themselves are federal. Even a letter that looks like a shakedown can call for a measured written answer rather than silence.

How can you respond to a patent demand letter?

The right response depends on what your checks turn up. These are the common paths, and more than one can run at the same time.

• Ask for specifics. Request the asserted claims, a claim chart and proof of ownership. This commits you to nothing.
• Deny with reasons. If the patent is expired, lapsed, or plainly does not read on your product, say so briefly.
• Negotiate. If the claim holds up after your checks, a license or a design change is one way to resolve it.
• Challenge validity. A petition for inter partes review asks the USPTO's Patent Trial and Appeal Board to reconsider the patent. It cannot be instituted if filed more than one year after you are served with an infringement complaint (35 U.S.C. section 315(b)).
• Notify partners. A supplier or platform that provided the accused technology may have duties under your contract.

General points about tone, and the rules that keep settlement offers out of evidence, are in our step-by-step plan for answering any demand.

Answering a patent letter through a California attorney

A short request for a claim chart is something a business owner can send without help. Patent letters raise harder questions when the sender has already filed suits, when a license fee is significant, when the accused feature came from a vendor, or when you want your position on expiration or non-infringement stated precisely and on the record.

Through Talk to My Lawyer, a licensed California attorney writes your response letter from the demand you received, your product details and your USPTO findings, and sends it on your behalf. For an infringement or validity opinion, talk to a registered patent attorney about your facts.