Patent infringement letters are sent when a patent owner believes someone is using, making, or selling their patented invention without permission.

If you receive a patent infringement letter, you should contact a Chartered Patent Attorney or intellectual property solicitor. Do not panic or contact the patent owner. Instead make sure you save all relevant documentation, including the letter, patent numbers and deadline dates associated with the demand.

Can I ignore a patent infringement letter?

There is no legal requirement to respond to a patent infringement letter, but if you receive notice of an alleged infringement, it is an opportunity for you to dissuade the patentee from pursuing their complaint further.

If you have received a patent infringement letter, stay calm and make a note of the deadline for a response, which will be included in the patent infringement notice. Resist the temptation to respond to the letter yourself. Instead, consult a Chartered Patent Attorney or IP solicitor. The letter is not proof of wrongdoing, so don’t be tempted to hide or alter product designs, records or communications.

“If you respond with a reasoned explanation as to why your product doesn’t fall within the scope of their patent, or why their patent isn’t valid, then that could close the whole thing down immediately,” explains Downing IP partner and patent attorney Michael Downing.

Consulting a patent attorney enables you to explore the possible defences open to you. Perhaps the patentee wasn’t aware of some aspect of your product or didn’t know about an earlier disclosure that you have access to.  In some cases, they might just be trying their luck, and a robust dismissal will be enough to deter further action.

Understand what you’re being accused of

Analyse the alleged patent infringement in consultation with your patent attorney. This will include checking the validity of the patent and whether it has a legal basis, as well as carefully comparing your product or process to see if there has been any infringement. Your patent attorney may also assess whether the complaint is worth defending. What is the value of this product to your business? Is it the ‘golden goose’ and needs to be defended at all costs?

A specialist patent attorney will assess the patent owner’s claim and advise you on the appropriate response. It may be that there is no arguable case of infringement, or a formal or procedural defect in the patent they are relying on. “Amazingly, sometimes people get this wrong, it’s quite the own goal when they do,” Downing says.

In some cases, modifying a product or process may be an option to consider. In others, your patent attorney might find mistakes in the examination history of the patent that can be taken advantage of, or you may be advised to make a settlement or discuss the opportunity to license the intellectual property.

Don’t respond before seeking professional patent infringement advice

Always seek expert advice when in receipt of a patent infringement letter. Never respond without the advice of a patent attorney or intellectual property solicitor as doing so can complicate your case and make it harder to defend. Contacting a patent owner without legal representation risks making accidental admissions that are difficult to row back from later. Any correspondence you send can be used as evidence in court later and could undermine any future legal arguments.

Instead, keep a cool head, and identify a reputable lawyer. You can do this through the Chartered Institute of Patent Attorneys (CIPA) Find a Patent Attorney tool or consult the government’s GOV.UK Intellectual Property Advice pages for more advice.

What happens next?

Once you have identified a reputable patent attorney or intellectual property lawyer they will review the accusation against you. They will assess whether there has been an actual infringement and advise you on the defences or courses of action open to you. 

They will then draft a response by the applicable deadline. Depending on the nature of the claim and the recourse open to you, in some cases settlements will be the preferred course of action over costly formal legal proceedings. However, your lawyer will advise you on what stance to take and when it is appropriate to take a more robust legal approach.

Downing says there are usually three potential courses of action, which he defines as fight, flight or invite.

• ‘Fight’ is when you decide to defend your product legally. You and your adviser will decide in which tribunal or jurisdiction you want the claim heard, and declare that the patent is invalid, or has not been infringed.
• ‘Flight’ entails pulling the product off the market and submitting an apology to the patent owner.
• ‘Invite’ looks for compromises in which both businesses can walk away with a fair deal. Your patent adviser will assess whether there is a commercial basis for suggesting a licence, or if there are other proposals that might be more beneficial than legal action.

Downing IP is a specialist intellectual property law firm with deep experience advising clients across the full spectrum of IP rights, including patents, trademarks, and design protection.

Downing IP supports the intellectual property interests of a broad spectrum of businesses from SMEs to large organisations and multi-national corporates. Founding partner Michael Downing has more than 30 years’ experience in intellectual property, with an engineering and metallurgy background.

Headquartered in Bourne End, Buckinghamshire, Downing IP has offices in Cambridge, Dublin and Silverstone and represents clients across the UK, Europe and further afield.