Priority applications – where should I file?

The priority year is a well-known and well-used feature of the patent system. In short, the priority year provides applicants with 12 months from the filing of an initial patent application, within which to file additional patent applications to the same invention in other countries or jurisdictions. This allows applicants to ‘plant a flag in the sand’ for their invention, while deferring the costs associated with multiple filings.

A further benefit is that the search report issued in respect of the initial priority application can generally be used to inform decision-making regarding additional filings to the same invention. For example, a positive search report may give an applicant confidence to proceed with an ‘international’ PCT application, whereas an applicant may choose to follow a more conservative filing approach in a small number of key territories (or not file at all!) if the search report cites potentially problematic documents.

The choice of where to file the priority application is therefore important, in that this dictates the cost and quality of the search undertaken. The searches provided by official offices can be classified as ‘low-cost’ and ‘premium’. Here we explore the searches offered by a selection of offices typically used for filing priority applications.

Low cost

The search fee at the UK Intellectual Property Office (UKIPO) is £150* (approximately 175 euros**) for an application with up to 25 claims. This is inexpensive in the context of search fees. However, the quality is generally still helpful in providing an overview of the state of the art – indeed the UKIPO are known to benchmark their search quality against that of the European Patent Office (EPO)[FN1]. In addition, the search report is usually provided within 6 months of filing the request for search, leaving plenty of time for consideration before the end of the priority year.

It is noted that if a subsequent PCT or European application is filed claiming priority from the UK application, a further search will be required. For example, for a PCT filed with the UKIPO, a further search fee of £1518* will be required for the EPO to carry out a more extensive search as International Search Authority. That is, first filing with the UKIPO does not avoid paying for a more expensive search but rather delays this until the end of the priority year.


The search provided by the EPO is widely regarded as being of high-quality. As such, it is often the first-filing office of choice for applicants relying on the search to help shape the patent filing strategy. However, the quality is reflected in the search fee of 1390 euros*, which is significantly more than the fees for the UK search described above. The EPO aims to issue the European Search Report within 5 months of filing the application.

It is noted that if a subsequent PCT application is filed claiming priority from the EP application, no further international search may be required depending on the overlap between the claims of the EP application and the subsequent PCT application. Often the initial EP search is used as the international search with the international search fee being waived accordingly. Put another way, most or all of the expense required for searching is likely to occur at the beginning of the process.

For applicants wishing for a premium search without the initial expense of the EPO search, there is a potential alternative. The Netherlands Patent Office (NPO) offers an international-type search that is carried out by the EPO. Interestingly, the fee for the international-type search is much lower than the search fee when filing with the EPO directly (794 euros and 1390 euros respectively*) despite both searches being identical in scope. As such, the NPO international-type search provides a cheaper option for applicants seeking a high quality search to help steer a subsequent filing strategy.

As with the EPO first filing, this international-type search from the NPO may be used as the international search for a subsequent PCT application or, similarly, as the European search for a subsequent European application. Although applications may be filed at the NPO in English, a translation of the claims must be provided in Dutch. As such, the cost savings of the NPO international-type search relative to the EPO search may be offset slightly by translations costs. However, there is no substantive examination before the NPO with the application granting automatically following completion of formal requirements.

The NPO does also offer a national-type search, which is inexpensive at 100 euros*. Although these national-type searches are often executed by the EPO, they will not result in the same fee reduction as the NPO international-type search later on.

Final comments

There is, of course, no single correct strategy regarding where to file priority applications and the approach may differ between applications. Applicants must consider how important the application is and how influential the priority application search will be in steering the follow-on filing strategy. These considerations may need to be balanced against company cash-flow and the importance of rights derived from the priority application itself.


* All fees provided are correct as of 19 May 2022. All search fees refer to online search fees
** All exchange rates provided are correct as of 19 May 2022


This article was prepared by HGF Patent Attorney Dr Craig Morrison and  Trainee Patent Attorney Dr Vincent Van Der Mark. Please get in touch if you would like to know more regarding formulating an effective filing strategy that works for your business.