Austrian entrepreneur A has developed a new, particularly lightweight and stable carbon fiber for sports equipment and wants to present it for the first time at an international trade fair in the USA next week. Since the entire professional world will be represented there, A plans to disclose all technical details in order to attract customers and investors. At the same time, he wants to secure patent protection in 20 countries, including major markets such as the US, China, Japan, and the most important European countries.
A is now considering filing a complete patent application in each of these 20 countries before the trade fair. This would require extensive translations, for example into Chinese, Japanese, and French, as well as the payment of all national office and attorney fees. The costs could easily run into six figures – even before it is clear whether the carbon fiber will actually be a commercial success. In addition, patent protection would be lost forever in all those countries where A does not file in time, because its own presentation at the trade fair would be considered the state of the art.
This is a big risk for A: perhaps the carbon fiber will not be successfully sold in all 20 countries, or it may turn out that competitors have already registered similar developments and the invention does not pass the novelty test. In this case, immense costs would have been invested in vain.
The right of priority was introduced at the end of the 19th century as part of the Paris Convention (PC). The background to this was the World's Fair in Paris in 1889: exhibitors should be able to present their inventions there without immediately losing patent protection in other countries. Since then, the right of priority has applied in almost all major industrialized nations, as the PC now applies almost worldwide.
In addition to the right of priority, the Paris Convention also stipulates that each country has the right to assess patent applications independently, i.e., it is not permissible to refuse to grant a patent or to declare a patent invalid on the grounds that another country has also decided against patentability.
Effects of the right of priority and priority period
The effect of the right of priority is that, after an initial application, e.g., in the home country, the inventor has one year to submit patent applications in other member states of the PCT. During these 12 months, the initial application is treated as an “option”: publications – including the inventor's own – and subsequent applications by competitors can no longer jeopardize the novelty of the invention. The subsequent applications are treated as if they had already been filed on the date of the initial application.
Instead of filing patent applications in 20 countries at the same time and incurring enormous translation and procedural costs, it is sufficient for A to initially file only one initial application in Austria. With this application, he secures a priority year of 12 months, during which he can present the carbon fiber worldwide at trade fairs and disclose all details without risk. Within this period, he can then decide which countries are worth filing subsequent applications in, depending on initial market reactions and financial possibilities. There are no costs for other countries (with the exception of Austria) at this stage.
In order to obtain protection abroad, the inventor first submits an initial application to a patent office of a member state of the Paris Convention (PC). This application secures the novelty of their invention and allows them to publish it or present it at trade fairs without risk. Within the following 12 months, they then have the option of filing further patent applications in any other PCT member states. These so-called subsequent applications are treated as if they had already been filed on the date of the initial application, provided that the priority right is expressly claimed.
After 11 months, A concludes that applications in the US, Canada, Australia, and Japan are worthwhile and justify the application costs. He therefore files subsequent applications in these countries within the 12-month period. In terms of the state of the art, these are treated as if they had already been filed on the date of the initial Austrian application. Publications, including his own trade fair presentation, or subsequent applications by competitors can no longer jeopardize the novelty of his invention during this period.
If this period is not used, the priority right expires. Any publication by the applicant or any third party after the initial application can then be considered prior art and destroy the novelty of a later application.
If A decides to apply for a patent in Germany only after 13 months, the date of the initial Austrian application no longer applies to this application, but only the new application date in Germany. This means that everything that has been published in the meantime—including the applicant's own presentation at the trade fair in the USA—now counts as prior art. As a result, the application in Germany lacks novelty and protection is irretrievably lost.
Finally, the right of priority also offers a small additional benefit in terms of duration. Since a patent always runs for 20 years from the filing date, this period is postponed by up to one year in the countries where the application is filed later. If the full 12-month period is used, the effective term of protection in these countries can be up to 21 years.
In Austria, where A filed the initial application, patent protection runs for the normal 20 years from the date of the initial application. However, if A files subsequent applications in other countries within the priority period—such as the US, Canada, Australia, and Japan—the 20-year term of protection there only begins on the date of the subsequent application. If A makes full use of the 12 months, the patent in Austria will expire after 20 years, while in the countries where subsequent applications were filed, it will remain in force for up to 21 years from the date of the initial application. This means that A effectively gains an additional year of patent protection in all these countries.
Formal requirements of the Right of Priority
The right of priority is a key means of securing international patent protection. However, there are clear requirements that must be met in order for the right of priority to be effectively claimed.
First, it is formally necessary to expressly assert the right of priority. This means that when filing the subsequent application, the applicant must inform the competent patent office that they wish to rely on an earlier application. The filing date and the country of the first application must be specified, and in some cases the application number must also be provided. In addition, many patent offices require the applicant to submit a certified copy of the first application. Some offices require this copy to be translated into the official language. This serves to verify that the content of the first application actually corresponds to the priority right of the subsequent application. However, it is not necessary to inform the patent office of the first application that foreign applications are being filed.
A first registered his carbon fiber invention in Austria and now wants to obtain protection in the USA, Canada, Australia, and Japan within the 12-month period. In order to claim priority rights there, he must explicitly refer to the Austrian initial application in each subsequent application and specify the filing date, the country, and, as a rule, the application number. In addition, the patent offices require a certified copy of the Austrian application (“priority document”), which in some cases—such as in Japan—must be translated into the respective official language. In this way, the offices check whether the claimed content of the subsequent application was actually already included in the initial application.
Another essential formal criterion is that the initial application must have been filed in a member state of the Paris Convention (PC). However, this is rarely a problem in practice, as almost all countries worldwide have acceded to this convention. Even for countries that are not officially part of the PC, such as Taiwan, there are often bilateral or multilateral agreements that have a similar effect to the priority right under the PC.
Austria, the USA, Canada, Australia, and Japan are members of the PC, so mutual recognition of the priority right is not a problem.
In addition, the 12-month period between the initial application and the subsequent application must be observed. This period is fixed and cannot be extended. This means that the subsequent application must be filed no later than the anniversary date of the initial application. If this period is exceeded by even one day, the right of priority is lost. As a result, the invention is no longer new due to the prior art published in the meantime. If, on the other hand, no prior art has been published in the meantime, the applicant can obtain a valid patent (with a later filing date).
Assuming that A has not publicly disclosed his invention, but has only worked on improvements in secret with business partners, he could still file patent applications in other countries after the 12-month period has expired. However, these would no longer be retroactive to the earlier Austrian filing date, but would only receive the new filing date. As long as there are no publications by A himself or by third parties in the meantime that destroy the novelty of his carbon fiber, A could still obtain a valid patent—but with a later filing date, which would shift both the scope of protection and the term of protection accordingly and could make possible interim applications by competitors dangerous. However, the publication of the application in Austria (18 months after the filing date) establishes the state of the art.
Another formal requirement for priority rights is that the applicant for the subsequent application also has the right to priority. Normally, the applicant has this right if he or she is the person who filed the initial application. However, it is possible to transfer the priority right to third parties, for example through sale. In this case, the transfer of the priority right must have taken place before the subsequent application was filed. Without this transfer, the priority right cannot be claimed, which is particularly important if a third party attempts to assert a priority right to which they are not entitled.
Suppose Austrian entrepreneur A has filed his carbon fiber with the Austrian Patent Office as an initial application. A few months later, B, a competitor, learns of this application and now wants to file a subsequent application in the US, Canada, and Japan, citing A's priority right. However, this would not be possible because B was never the owner of the initial application and A did not transfer the priority right to him. Without priority rights, the application would not be new due to the publications by A. (In addition, B faces a fundamental problem of entitlement in this situation: he would not be allowed to apply for a patent on an invention that does not belong to him at all, and A would be entitled to revocation.)
However, if A transfers the priority right to B, the latter can assert the priority right. His subsequent application would be treated as having the filing date of the first application. Even if A has already disclosed his invention, this disclosure would not be considered prior art.
Material requirements for Priority Rights
For the priority right to remain effective, the content of the invention must remain essentially the same between the first application and the subsequent application. New technical features that were not included in the first application may be added to the subsequent application, but the applicant loses the priority right for these new features.
A first registers his particularly lightweight carbon fiber in Austria, thereby securing the right of priority. However, within the priority year, he continues to work on the technology and additionally develops a special resin coating that makes the fiber water-repellent and extends its service life. This new feature was not included in the initial application. If A now submits a subsequent application after 10 months, he can claim priority for the original carbon fiber, but not for the newly developed coating. The filing date of the subsequent application applies to this additional feature.
If A were to publish the coating during the priority year and only apply for it afterwards, this improvement would no longer be new and therefore no longer eligible for protection. It therefore makes sense to keep further developments such as new inventions secret until a patent application is filed if you want to obtain patent protection for them.
Priority rights can only ever be linked to the first application in which a particular invention was described by the applicant for the first time. A subsequent application may therefore only be based on this initial application.
A files an application for his new invention on January 5 in Austria and on January 8 in the US. When A forgets to file subsequent applications on January 5, he tries to claim the priority of the US application for his subsequent applications. However, priority rights can only be claimed from the Austrian application. The subsequent applications are given the priority date of their filing date (one year after the initial application). Publications in the meantime may be detrimental to novelty.
However, it is possible to postpone the patenting process altogether by withdrawing the initial application before its publication and not claiming any priority rights, so that this application has virtually no legal effect. A later application can then be the first application again and form the basis for priority rights.
A initially registers his novel carbon fiber in Austria in January 2025. This means that the 12-month period for claiming priority rights runs until January 2026. In 2025, A notices that the market is not yet ready for the technology. He withdraws the application. When A resubmits the application in 2028, he can claim priority rights from this application, for example for a subsequent application in 2029.
Due to the first-to-file rule, it is also not possible to artificially extend the 12-month period by means of a series of “chain applications” by repeatedly submitting new applications and claiming the priority of the previous ones. The Paris Convention expressly provides for only a one-time priority period of 12 months. After this period has expired, backdating is no longer permitted – later applications will then only receive their own filing date as the relevant filing date.
A initially registers its novel carbon fiber in Austria in January 2025. This means that the 12-month period for claiming priority rights runs until January 2026. Now, in December 2025, A has the idea of quickly filing a second application in Austria and then using this as the basis for foreign applications in order to “extend” the period. However, this would not be permissible: for subsequent applications in the US, China, or Japan, only the first application from January 2025 could be used as priority. The second application in December 2025 would not open a new priority year. So if A were to file the US application in February 2026, the priority right would already have expired and the filing date would be February 2026 – with the risk that interim publications would destroy the novelty.
First-Page Indications
Cover sheets of patent applications and granted patents are important sources of information that provide a quick overview of the relevant data of a patent. In addition to the title of the invention, the applicant, and the inventor, they also contain information on the priorities of the application. The priority information is always clearly noted on the cover sheets. They indicate when and in which country the initial application was filed and whether priority rights were asserted. The priority information is particularly useful for drawing conclusions about the international scope of an invention. The priority information can be used to determine in which countries the applicant plans to obtain protection for the invention. This information provides insight into the applicant's patent strategy and shows whether and how the invention is protected internationally.
The first page of the German patent specification (initial application, left) shows the publication number DE 10 2024 104 481 A1, the filing date 2.10.2022, and the note that the patent specification originates from the German Patent and Trademark Office. In the publication of the European subsequent application (right), the details of the German first application are published under INID code 30. The European application therefore claims the priority right of the German application. Since notification of a subsequent application filed with the European Patent Office is not mandatory for the German Patent Office, there is no reference to this in the publication of the German first application.
The right of priority not only influences the relevant priority date of a patent application, but also postpones the 18-month publication period. In the event that a right of priority is claimed, this period begins on the filing date of the initial application, so that all subsequent applications are also published earlier, i.e., no later than 18 months after the filing date of the initial application.
Both the German application and the US application will be published 18 months after the filing date. Due to the different publication practices (the DPMA and EPO each publish on a specific day of the week), the publication dates may differ. However, both publication dates, August 20, 2025, and August 21, 2025, are shortly after the end of the 18-month period, which expired on August 19, 2025.
To examine the territorial scope of patents that are linked by the same priority right, there are special search tools, namely the so-called family search. Such a family search lists all applications worldwide that are based on a common initial application. It also shows in which countries the invention is protected and what further developments or publications there are in connection with the original initial application.
