If you have had any dealings with IP, you will probably have heard the term “priority”. Here we explain more about what that terms means, in relation to patents. We explore the nature of priority rights, how they can be used to an applicant’s benefit, and potential pitfalls.

What is priority?

An applicant who has filed a first patent application for an invention has, for the purpose of filing further patent applications in respect of the same invention, a right of priority for a period of 12 months after the first filing. The right to priority is enshrined in the Paris Convention, and recognized in regional and national patent laws, including the UK Patents Act and the European Patent Convention. 

The practical utility of this right lies in the fact that the earlier filing date of the first patent application (the “priority application”), rather than the filing date of the later application, determines what prior art can be used to assess the patentability of the later application. Thus, intervening disclosures that occur between the filing date of the priority application (the “priority date”) and the filing date of the later application cannot be used against the later patent application. 

Who can claim priority?

The right of priority belongs to any person who has filed a first patent application for an invention, or their successor in title. The person can be a natural or legal person, i.e. an individual or a company.

For a valid priority claim, it is important that the applicant of the later application is either the same as the applicant of the priority application, or is their “successor in title” when there has been a transfer of ownership of the priority application prior to the filing of the later application.

Why file a priority application?

It is common practice for an applicant to file an initial priority application in their home country (e.g. a UK national patent application), then follow up within the priority year with further applications in other countries (or an international patent application) which claim priority from the initial application. 

The benefits of this approach include:

  • securing an early priority date at a relatively low initial cost, after which the invention can be published;
  • delaying the major costs associated with a wider patent filing program for 12 months, which can buy time to seek investment;
  • a pending priority patent application can help to attract investment;
  • it is possible to get a UK priority application searched within the priority year. The search results can provide a useful indication of the likelihood of getting a patent granted, prior to incurring the expense of a wider filing program. The search results can also be used to determine whether any amendments should be made to the patent application;
  • the priority year can be used to further develop the invention, generate additional data and finalize the content of the application prior to a wider filing program

Do the applications have to be identical?

In short, no. However, the later application must be in respect of the “same invention” as the initial priority application for a priority claim to be valid. 

Under European patent law this means that for a patent claim in a later application to be entitled to priority, the subject matter of the claim must be “directly and unambiguously derivable” from the priority application as a whole. 

It is not uncommon for a later application to contain a mixture of patent claims which are entitled to priority and claims which aren’t, for example when development of the invention during the priority year has led to new aspects of the invention being discovered and added to the later application. In this case, different dates are used to assess the prior art for the different claims – whilst only publications preceding the priority date can be cited against the priority-entitled claims, intervening publications made between the priority and filing date of the later application can be cited against claims that are not entitled to priority.

In practice it is generally safe to add to the later application additional examples and data that support the existing disclosure of the priority application. When additional subject matter beyond this is added to the later application it is imperative that this is done in a way that preserves the priority right for as much of the later application as possible. Your patent attorney will be able to advise you on the best way to achieve this.  

How do you claim priority?

Priority is not an automatic right. Rather, it has to be “claimed” when filing the later patent application. 

This is done by filing a declaration of priority providing basic details of the priority application. The declaration is ordinarily filed at the time of filing the later application, but can, in certain circumstances, be filed up to 16 months from the earliest priority date. Depending on the countries concerned, it may also be necessary to file a certified copy and/or a translation of the priority application. These are formalities that in practice will be taken care of by your representative. 

Can you claim multiple priorities?

Yes. A later patent application can claim priority from more than one priority patent applications filed within the preceding year. Each of the claims of the later application will then be entitled to the priority date of the earliest priority application to disclose its subject matter. 

Where an invention is developed during the course of the priority year following the first filing, one or more further priority applications are often filed to obtain the earliest possible priority date for any additional subject matter. Then any patent application(s) filed at the end of the priority year should be a finalised version containing all the subject matter and claiming priority from all of the previous applications. 

What can go wrong?

Unfortunately, quite a lot! Whilst priority is a simple concept, in practice there are several intricacies which can trip up an applicant. In the worst-case scenario this can result in the complete loss of the priority right, which may prove fatal to the later application due to intervening prior art. 

The main pitfalls to watch out for are:

  • the priority application is not the first application for the invention –the priority application must be the earliest application by the applicant for the subject matter. Where an even earlier application exists, this must be withdrawn, abandoned or refused under very specific circumstances for a later application to validly serve as basis for a priority claim;
  • the applicant for the later application is not the same as, or the successor in title to, the applicant for the priority application – issues often arise where a transfer of the priority application has not been completed correctly, or has not been completed prior to, the filing of the later application, or where co-applicants are involved. These issues can rarely be rectified after the fact, and so it is imperative to get them right;
  • the later application is not in respect of the same invention as the priority application – claims that have been amended, introduced or broadened in the later application may not be entitled to priority, depending on the specific circumstances

For tips on how to avoid the pitfalls and get priority right see our article here

This article is for guidance only and should not be taken as legal advice. For advice on specific cases please contact the patents team.