A US patent application may be filed on a number of bases. Most applicants think of directly filing an original, non-provisional patent application in the US. However, roughly half of the patent applications actually are filed by non-US entities and have foreign priority claims. A foreign priority claim allows a later-filed application to adopt the filing date of an earlier-filed application, which can be valuable during examination of the application. A foreign priority claim is proper when the US application is filed under the Paris Convention or as a national phase entry under the Patent Cooperation Treaty.
When an applicant files a US application with a foreign priority claim, a copy of the foreign priority application must be submitted to the US Patent Office. The copy must be a certified copy, which means it has to be reviewed and stamped by the foreign patent office. Foreign priority documents do not need to be provided at the time of the filing, but they do need to be provided. So while timing is not of the essence, compliance is important.
There are two mechanisms for providing the priority documents. The first mechanism is simply filing and submitting the certified document with the US Patent Office. There are fees involved with obtaining a certified priority document, and it takes time to request the document, wait for it to arrive, and then ship it to the office.
The second mechanism uses the Priority Document Exchange program. Some patent offices around the world have subscribed to the PDX program, and if the earlier-filed application was filed in one of the countries, the applicant can request that the office of earlier filing electronically transmit the earlier-filed application to the office of later filing. Provided that foreign filing license and other requirements are complied with at the earlier office, that office will transmit the application. There is no governmental fee for such a request, and it can save considerable time and administrative work.