New inventions in the priority year
A common practical situation during the priority year is the further development of the invention. This raises the question of how to deal with new technical features that are only developed after the initial application. Priority rights generally only apply to those parts of the invention that were already fully disclosed in the initial application. If new features are added during the priority year, the filing date of the subsequent application applies to these. It is therefore possible that a patent claim that exclusively targets the original part of the invention will continue to have priority rights, while a new claim for the added feature will only be assessed from the date of the subsequent application.
Austrian entrepreneur A files his first invention in January 2025 – a particularly lightweight carbon fiber for sports equipment. In April 2025, he develops a second invention based on this, namely a special braided structure that makes the fiber even more stable, and also submits an application for this to the Austrian Patent Office. Finally, in September 2025, a third application follows: a resin coating that makes the carbon fibers water-repellent and extends their service life.
In December 2025, A decides to file a subsequent application claiming all three inventions together. Patent claim 1 claims the carbon fiber. Patent claim 2 claims the combination of carbon fiber and braided structure, and patent claim 3 claims the combination of carbon fiber and resin coating.
He asserts three priorities for the applications: Patent claim 1 for the carbon fiber has a filing date in January, patent claim 2 concerning the special braided structure has a filing date in April, and patent claim 3 concerning the resin coating of the carbon fiber has a filing date in September.
Each invention is therefore “backdated” to the date on which it was first filed with the patent office. This means that the state of the art at the time of the respective first application is decisive for the novelty and inventive step. It is therefore possible that individual patent claims in the same subsequent application may have different priority dates.
Strategically, this means that any additional invention that is not yet described in a patent application must be kept secret like a new application in order to avoid creating prior art before the priority date of the respective additional invention.
If, for example, A has already developed the special braided structure in February and publicly displays textiles with this braided structure in March (e.g., through sale), the prior art from February precludes patent claim 2, which can only be dated to April due to the filing date of the subsequent application. A's own sale thus precludes patent claim 2 from being novel.
