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Guide to patent application grace periods and disclosures

The patent system is pretty clear about the fact that an invention, to be patentable, must be new. The details vary between different countries’ laws, but the basic principle is that it must never have been available to the public, in any form, anywhere in the world. But, as with most rules, there are exceptions.

The law has to recognise that there are circumstances where the novelty of an invention has been lost through no fault of the inventor. In addition, some countries see fit to introduce just a little flexibility into what would otherwise potentially be a harsh rule.

What criteria must your invention have for you to be able to file a patent?

Novelty is the first and most fundamental requirement for anyone looking to file a patent. In the UK, and other European countries, it must also involve an inventive step (meaning it is not obvious, which is how the US law formulates its equivalent requirement) and be capable of industrial application. Of these three requirements, novelty is the one that you could damage or destroy: the other two are present or not, and nothing you do can change it.

In the UK and Europe, the novelty of an invention is judged by comparing it with the state of the art, and the state of the art is defined in extraordinarily wide terms. In effect, it means the sum of human knowledge – unless that knowledge has not been published in any way.

How to protect your idea if you decide to disclose it to another party

To preserve the novelty of your invention, you must keep it secret. One very valuable tool that will help you do this is the non-disclosure agreement, or NDA (or Silicon Valley Handshake, as it is sometimes called). It’s not a perfect solution, because many industrial companies won’t sign them as a matter of policy, fearing that the person offering them their new invention is only going to tell them about something they just developed independently themselves – you can imagine how that could create problems. But at the right point in the process, an NDA is pretty essential (and we can provide one that’s tailored to your requirements, to save you trying to find a suitable document on the Internet which will usually turn out to be American and therefore not quite right for the UK).

You don’t always need an NDA, though. It’s already effectively part of your relationship with your intellectual property solicitor, or patent attorney, so you don’t need to get them to sign a document which probably would not go as far as their professional obligation of confidence anyway. With other professionals, such as bankers, and certainly with prospective partners or licensees, it’s crucial to get an acknowledgement of the confidentiality of your information.

What if you have told your friend in the pub more than you should? A judge would ask whether the friend – or ex-friend, perhaps – understood that the information you were sharing was confidential. The law considers the conscience of the recipient of confidential information, not the form of any obligation you have placed on them, and even an unspoken obligation can be enforced, if its existence can be proved: but it really is not a good idea to get into that position. Use a written NDA, or keep quiet.

Don’t let anyone see your invention, either. If you’re the classic inventor in your garden shed, make sure you keep it locked. More to the point, don’t try out your invention where the public can see it, for example on a public road or in a field with a public footpath running beside it. It makes no difference that no-one who could understand your invention actually came along and saw it in action – the law is only concerned with the fact that you put it in a place where that person would be able to see it.

What should I do if I have already disclosed my invention?

If you have let the cat out of the bag, and disclosed your invention before you filed a patent application, you need a grace period to save you. Unfortunately, the UK does not give one, except in the limited case of disclosure at an international exhibition. You can still file an application, and the chances are that the examiner will not pick up on the disclosure, but if you are granted a patent it is going to be vulnerable to a challenge if you have to enforce it.

What if you did disclose your invention at an international exhibition? Under UK law, you get six months from the date of the disclosure in which to file an application for a patent – your disclosure will be classed as “non-prejudicial”. When you file your application, you must include details of the exhibition. But few exhibitions qualify: only an exhibition which falls within the terms of the 1928 Convention on International Exhibitions (as modified by the 1951 Protocol) is regarded as an international exhibition. It must satisfy stringent conditions – it must run for at least three weeks, and invitations to participate must be issued at government level through diplomatic channels. If the Patents Journal states that a particular exhibition qualifies, that is conclusive evidence. Trade fairs and events organised regularly by particular industries are unlikely to qualify.

Although this is an area of patent law that has not been harmonised at the international level, the European Patent Convention does mean that the rules about international exhibitions are common to most European countries.

Under the America Invents Act of 2011, publications by the inventor within one year of filing (inventor's "publication-conditioned grace period") are non-prejudicial and do not form part of the state of the art when the application is examined. This applies to both provisional and complete applications. This may be useful not only if your first filing is in the US, but also if your US application claims priority from (say) a UK application, because the US grace period would run from the priority date (the date of filing in the UK, in this example). A disclosure in the 12 months prior to the UK filing would be non-prejudicial under US law, and as the US filing could be made up to 12 months after the UK filing that makes an effective grace period of two years. The UK application would fail because of the prior disclosure, but at least you would have salvaged a US patent from it.

South Korea offers a 12-month grace period similar to that in the US. China has rules rather similar to those in the European Patent system (and therefore the UK), with the addition of inventions published for the first time for the purpose of public interest when the country is in an emergency or extraordinary situation. This last rule came into effect on 1 June 2021, which gives a good idea of what prompted it.

Australia has a 12-month grace period similar to that given by US law, although it only benefits complete applications and not provisional applications. New Zealand introduced a 12-month grace period in 2019, to comply with the Comprehensive and Progressive Agreement for Trans-Pacific Partnership: Canada has had a similar grace period for many years.

What are happens if another person publicly discloses my invention?

If you gave permission for this person to disclose your idea, you get no special protection. But if someone disclosed your idea without your consent, you may have a 6 month grace period in most European countries. Under the European Patent Convention, with which UK law complies, any public disclosure that results from an evident abuse in relation to the applicant or inventor, such as by the disclosure being in breach of confidentiality or based upon unlawfully obtained information, is non-prejudicial.

Most of the countries that give grace periods similarly cover unauthorised disclosures by third parties.

Should I file a patent application before I disclose my invention?

Yes! Filing a patent application fixes your priority date, and no disclosure that happens after that (whether by you or anyone else) will affect your application. File early to avoid the invention being disclosed, or anticipated by another inventor working independently of you, but don’t file too early and miss some feature of the invention that you don’t fully appreciate at the time.

Even after you file the application, in the UK system it is not published for another 18 months. It’s therefore open to you to withdraw the application before then and refile without losing the crucial novelty of the invention, perhaps to give you more time to raise finance and regenerate the priority date: but be aware that this is a risky strategy, because someone else might have filed a conflicting application in the interim or the invention might have been disclosed and therefore lost its novelty.


While some countries’ patent laws give inventors protection against any disclosure of their invention prior to filing for a patent, in the UK and the rest of Europe it only works in very limited circumstances. The rules are complicated and you need to know your way round them to be able to take advantage of them – but the best advice is always to play your cards close to your chest, at least until you have an application filed, so you avoid having to search for some way to save your prospects of getting a patent.

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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