Patent infringement claims – How to enforce your patent rights

Patent infringement claims – How to enforce your patent rights

'I believe another business is using my patent without permission. What should I do?’

It is important to act decisively when dealing with someone who has infringed your patent. Failing to do so could threaten the commercial viability of your business. A patent protects your invention. If your business’ unique selling point is that you are the only source of your invention, then allowing it to be copied should not be an option.

Are you experiencing problems with a business that is using your patent without permission?

Common types of patent infringement include:

  • Producing a product based on your patent
  • Using a process protected by your patent
  • Importing your invention without authorisation
  • Selling or attempting to sell a product based on your patent without consent

As some cases require immediate action, we suggest you contact a IP lawyer as soon as possible for advice.

Practical considerations for businesses

What evidence do you have to support your claim?

We encourage clients to start collecting supporting evidence before you seek legal advice. Ideally, any evidence should be clearly dated for reference. Typically, you will be making a trap-purchase of a sample product or asking questions about a process that is being offered to the market. It is important to collect evidence at an early stage to make sure that your initial meeting with your lawyer is productive. Our experienced patent lawyers will be able to quickly review any supporting evidence before your first consultation. We will then help you devise a plan that will stop the alleged infringement.

What stage of the patent process are you at?

Firstly, is your patent published? This is unlikely if it is less than 18 months since the earliest priority date. Secondly, has it been granted yet in any territory? You may have progressed an initial UK patent to substantive examination and be close to grant whilst your filings for other countries may still be at the “placemarker” PCT stage or the earlier stages of regional/national examination.  

Decisive action in the UK will be effective in such a situation but you can expect the infringer to make representations to the EPO and other examining offices suggesting your invention is not truly patentable as drafted.

What is the risk to your business?

Is the patent infringement having a real commercial impact on your business? Does the use of your patent threaten the long term viability of your business? Realistically, given how much money you have access to, and how much money the infringer has, for how long can you fund this claim?  If you begin your case will your budget only stretch to the letter-writing stage? All are practical considerations for business owners.  Sometimes an infringer can replicate the patented invention but lacks the skills to make a meaningful offer to the market – their infringement then fizzles out of its own accord. To give a contrary example, sometimes your toleration of an infringement can rule you out as an attractive investment for venture capital firms – investors tend to be very focused on your ability to monopolise the supply of your product or process, and with good reason, as they do not want to invest money in one company to drive technology forward, only for a different company to succeed.

Should I try to resolve the issue?

Although is it tempting to contact the infringer yourself, we advise against this, as a patent infringement is a serious allegation. Any correspondence must be carefully worded and the correct procedures must be followed. All too often we find that business owners compromise themselves by attempting to resolve an issue themselves. There are “threats” provisions in the patents act which increase the danger.  However, sometimes there is a commercial proposition such as cross-licensing which can work to the mutual benefit of you and the alleged infringer. Confrontation is not always inevitable.

How can I stop someone using my patent without my permission?

You will almost always send a solicitor’s letter before beginning infringement proceedings.  That letter will put the infringer on notice of your claim (particularly important if the patent is published but not yet granted). The first or second letter will include a claims chart, setting out details of your independent claims as drafted and showing how the infringer’s product or process replicates every subdivision of each independent claim (or dependent claim if necessary). To put this in layman’s terms, you need to show that the infringement “ticks every box” of at least one of your claims.

The response to the letter may compliance, a settlement offer, denial, a counterclaim that your patent is in fact not valid, or a combination of all of these. At this point your solicitors’ knowledge of the specialist rules of court concerning patent litigation will come into play.  It is not too soon to consider what expert evidence will be required and what if any experiments a court might order if the matter proceeds. Many of the points that a court consider are decided on the basis of experts’ reports on what people with the relevant skills knew at specific dates determined by statute. These tests are strictly defined and can be very frustrating for an inventor who is the world’s leading expert on his or her particular invention. Choosing the expert is therefore a critical decision and cannot be taken too soon.

If you decide to go ahead, we will guide you as to whether to use the low-cost IPEC court or a higher court qualified to hear patent cases. The case officially starts when the court stamps your claim form (a straightforward document) and you serve it on the other side. The first real expense will be the drafting of your “Particulars of Claim”, the contents and level of detail for which depend partly on the court you have chosen.  We will typically bring in a barrister to draft the Particulars of Claim and again, choosing the right barrister is a critical part of the case.

If your opponent defends, expect to find a counterclaim accompanying the defence alleging that your patent is not valid. That counterclaim is the Defendant’s to fund, they will be expected to provide expert evidence and experiments.  The filing of the counterclaim creates a settlement opportunity because the two parties can now take more informed advice about their prospects for success.

If the exchanges of statements of the parties’ cases do not bring about settlement, the court will summon the parties for a case management conference at which the judge will hear any procedural applications and make crucial decisions as to how many witnesses of fact, expert witnesses and experiments will be needed in order for the court to determine the case justly at trial.  The next months are then dominated by assisting the witnesses in the preparation of witness statements, which are often lengthy, and in assessing the witness statements provided by the other side. Again, this exchange of evidence creates a logical settlement opportunity as now the relevance and weight of the other side’s evidence can be weighed, and your own barrister can be very helpful in providing an objective assessment of your own evidence.

Finally, if the case still does not settle, it proceeds to trial. It is unusual for a case to get this far but sometimes the commercial basis for settlement simply is not there and the best course is to get a judge’s decision. If you win at trial, you can expect to be awarded a proportion of your costs, the amount of can be influenced by decisions you made on our advice at the very early stages, and for there then to be a second hearing to assess what damages you should receive. It is not unusual at this point for the loser to appeal (as there may be commercial reasons to avoid a final judgment being published) but the courts will often refuse to allow the case through the appeals process unless there is debate about whether the judge applied the right legal tests to the facts in the right way. 


Patent infringement is a serious allegation. Ignoring the infringement is not an option but litigation is not always feasible or desirable for SMEs. You need act decisively before the situation becomes worse. Our team of patent lawyers can act on your behalf, using our experience to help you take action against the alleged infringer.

About our expert

Lindsay Gledhill

Lindsay Gledhill

Intellectual Property Partner
Lindsay Gledhill is an Intellectual Property Partner at Harper James. She has specialised in intellectual property exploitation and dispute resolution since 1997. She trained and qualified in Cambridge’s top intellectual property firm during the 'dot com boom', then spent four years at top 50 firm, Walker Morris.

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