When to file a patent application

When to file a patent application

This article discusses when to file a patent application for a new invention. This is not about the decision whether to do so - we have a separate article on whether to file a patent application. This article is only concerned with the timing of filing a patent application and lists a number of issues to take into account.

1. To obtain a valid patent, your application must include sufficient information about the invention

It is a requirement of UK and European patent law that a patent application must provide an enabling disclosure, which is sufficient to enable third parties to reproduce the invention without undue burden. You therefore need to consider whether you can already provide an enabling disclosure of the invention or whether more research or development work will be required first.

2. Further research - more often an issue in some technical fields than others

It is more common to decide that more research is required before a patent application can be filed in fields such as chemistry and the life sciences than in other fields. With some therapeutic inventions, for example, it may be necessary to include evidence to demonstrate a required therapeutic effect and this requirement will sometimes lead to a delay in filing a patent application while data is obtained.

However, for many inventions in engineering (for example), once the idea can be expressed, writing an enabling disclosure is easy enough and there is no requirement to wait for the invention to be put into practice. Sometimes little more than a brief explanation of an idea or a couple of sketches can be readily bulked out to allow a properly enabled patent application to be prepared. Note that there is no general legal requirement to have actually carried out an invention when you file a patent application. The requirement is to be able to explain how it can be carried out to others skilled in the art.

3. To obtain a useful patent, it is necessary to understand the key features of the invention

A patent application includes claims which define the scope of protection sought. A good patent application includes the basis for broad claims and also for a range of narrower claims, useful as fallback positions if the broader claims are unpatentable. You cannot add anything to a patent application once it has been filed. It is therefore necessary to properly understand what is the invention that has been made in a broad sense and also to understand which more specific features could be important when a patent application is being drafted.

Sometimes, if a patent application is filed too soon, it later turns out that the actual invention which has been made is different to what was understood at the time of drafting. Alternatively, the invention may have different applications to those originally considered, and so the claims that were drafted may turn out not to be appropriate to protect what is eventually found to be important. It follows that there are times when a patent application should be delayed until the invention is properly understood. That being said, we are used to finding that technologies and their applications change, and we take this into account in the applications that we draft, and it is usually more important to not unduly delay filing a patent application, bearing in mind the possibility of filing supplementary patent applications in the first year (see point 11 below).

4. You must file a first application before you make a non-confidential disclosure

It is a (fairly) well-known basic feature of the patent system that you need to file an initial patent application before you disclose an invention, or your invention will no longer be new and inventive and so no longer patentable*. Although it remains preferable to avoid non-confidential disclosures even after an initial patent application has been filed, there are commercial situations where non-confidential disclosures must be made at specific times. In such cases, the decision when to file is simple as the specific time of the non-confidential disclosure provides a deadline by when you must get an initial patent application on file.

(* Some countries have grace periods allowing an application to be validly filed for a limited period of time after a non-confidential disclosure in specific circumstances. Grace periods should never be relied on but if a disclosure has taken place do check whether a grace period is available in any important territory).

5. Risks of breach of confidence

You may be concerned that there is a risk of your ideas becoming public even if the ideas are in principle being kept confidential. For example, you might be concerned about the risk of employees moving to competitors and taking your ideas with them. Another situation might be that you have discussed the idea with a third party under a non-disclosure agreement but you worry that the third party may be careless with the idea, or even try to protect it, or something similar to it, themselves. These circumstances would prompt early filing of a patent application, not only to avoid a risk of the idea becoming unpatentable due to it becoming public before you file a patent application but also because your patent application may later serve as useful evidence as to what was known to you at the filing date of the application.

6. The "race to the Patent Office"

The history books include various rushes to be the first to protect an idea, for example the famous race between Elisha Gray and Alexander Graham Bell to invent and patent a practical telephone. Occasionally circumstances arise where it is genuinely critical to get a patent application on file urgently because others may file similar patent applications imminently. However, in practice, particularly for inventions that could have been made at any time in the previous few years, the precise day on which a patent application is filed is only rarely critical and it is usually preferable to take the time to think carefully and act strategically.

7. The timing of your first patent application determines the timing of future actions and costs

When you file an initial patent application for an innovation you start a clock running. Usually, you will have filed the initial application in a single country, and usually, you will have until one year from the filing date of the initial patent application to file applications abroad with a "priority claim". The initial application and any other applications which claim priority from it are referred to as a "patent family". This legal framework means that when you file an initial patent application you determine the timing of future costs; for example, there will usually be costs to file applications in other countries (or internationally) with a priority claim one year later; usually there will be costs for examination by IP Offices which peak 3 to 5 years later. You should check the amounts of these costs and where they fall relative to expected funding rounds or sales income before deciding on a filing date.

8. The timing of your first patent application determines when your ideas are published

Furthermore, in the normal course of events, your family of patent application(s) will be published 18 months from the filing date of the initial patent application. This publication starts provisional protection in the UK and Europe (publication is the earliest date to which damages for infringement might be retrospectively awarded) but means that the contents of your application will become available to others to read on the internet.

To your advantage, when your application is published, it becomes full prior art taken into account when the UK or European Patent Office examine the inventive step of third party patent applications with a priority date after your publication date. However, to your potential disadvantage, your patent application will become full prior art taken into account when the UK or European Patent Office examine the inventive step of any of your own future patent applications with a priority date after that publication.

9. But there is the possibility to withdraw patent applications before publication

Applicants may be worried that the publication of their application will disclose important confidential information - and as we explained in the first point above, it is necessary to provide enough information in a patent application to enable others to reproduce the invention. This can be a very real concern. However it is also important to appreciate that a deliberate feature of the patent system, at least in the UK and Europe, is that you should receive an official search report before your application is published. In the normal course of events, you will have the opportunity to review this search report, to assess the prospects of obtaining broad patent protection, and to make a decision as to whether to continue. You can then let the application be published if it appears that you are likely to obtain broad patent protection. However, if the search report finds very relevant prior art and it looks unlikely that you will obtain the protection you initially hoped for, then you will usually have an opportunity to withdraw your patent application in time to prevent it from being published. (Note that there are very specific deadlines, which vary between Patent Offices, by when applications must be withdrawn to prevent publication and you should flag to your patent attorney if you are seriously considering withdrawing an application in time to prevent publication, so that the deadlines can be monitored).

10. You might wish to delay while a patent search is carried out

Where time and budget permit it can be helpful to have a patent search carried out to establish the likelihood of obtaining a patent before incurring the cost of drafting and filing a patent application. Sometimes a better patent application can be written when a search has been carried out as the claims can be crafted to distinguish carefully over the closest prior art. Nevertheless, many applicants who know their field, or know they anyway wish to file a patent application for commercial reasons, omit this step and wait for the results of the official searches which are carried out as part of the patent application procedure.

11. Bear in mind that you can file supplementary patent applications - but only for so long

As stated above, initial patent applications are usually filed in a single territory only and there is a deadline of one year from this initial filing date to file applications in other territories with a priority claim. You may never add anything to a patent application once it has been filed, but within this first year of the normal patent application process, you can file one or more supplementary patent applications with more information about the invention. It is then possible to progress a single patent application containing all the information disclosed in the initial and supplementary applications by claiming priority from each of the earlier applications.

In this case, where a patent family contains subject matter introduced at different times, individual claims have to be new and inventive as of the filing date of the first application to have included the subject matter. This means that - provided you keep the invention confidential - you can readily include new developments into new filings in the same patent family during the first year, thereafter proceeding with a single patent application per territory. It is therefore quite common to file an initial patent application promptly to obtain a priority date for key subject matter and to use supplementary applications to file more information, to support additional claims. This can be very helpful in cases where an invention is still being developed.

Once the first year is over, if you wish to include any more subject matter about the idea in an initial patent application, you will have to start a whole new patent family which does not claim priority from the initial patent application. This will often lead to a large cost increase as you require two patent families where you might have rolled various ideas into a single patent family if the first year had not passed.

However, even once the year has passed then, for the following six months, you can file a new patent application to start a new patent family before your first patent family is published. At least in the UK and Europe, the second patent family need only be novel over the first patent family (i.e. inventive step is not considered). However, once the first patent family has been published, any subject matter which is included for the first time in a subsequent patent application has to be both new and inventive over the first patent family.


It is often possible to proceed with a patent application fairly quickly after an invention has been made, but it is usually preferable to think carefully about when and what to file than to rush a patent filing. If an invention is being actively developed then it is often possible to start the process by filing an initial patent application promptly and then to follow up with supplementary patent filings in the following 12-month period. However, there are circumstances, often in the chemical and life sciences fields, where it can be important to conduct research and development activity before starting the patent application procedure.

Generally, if a potentially inventive idea has been made, we would recommend discussing it with a patent attorney at an early stage to determine whether it is ready for patenting and to make a plan. If you would like to discuss an idea and an appropriate patent filing strategy to protect it, please feel free to contact us.

Author: Alistair Hindle, European Patent Attorney and Chartered Patent and Trade Mark Attorney

Related articles