Many changes have come to the patent system recently, particularly since September 2012 and even more so since March of this year. One of the most overlooked aspects relates to the claiming of priority to a foreign patent application.

For patent applications filed prior to March 16, 2013, an applicant pretty much has the ability to file a priority document up until the issue date of his patent application.  

Before we get to the recent changes in the rules, What is a claim of "priority" and a "priority document"

A claim of priority, and thus the need for a priority document, allows a patent applicant to claim the date of an earlier patent application filed in a foreign country for his US patent application.  Similarly, a US applicant can claim his US filing date as a priority date for a foreign patent application. 

The claiming of such an earlier date would allow  an applicant to "win" over another applicant that files a patent application with the United States Patent Office after his claimed foreign "priority" date but still before his US patent application filing date.   In this case, the foreign patent application has "priority" over the latter filed US patent application in that the claim of "priority" allows the latter filed US patent application which claim such "priority" to win over the application which was actually first filed at the US Patent Office.

The long and short of the above is that for a foreign applicant (and a US applicant in foreign countries) a claim of "priority" to his home country patent application allows him to "win" over others which file after such a home country application is filed even if it is before the time of the actual US application.

This brings us back to the recent changes in US patent rules which require that a certified copy of such a "priority" patent application from the Patent Office office of such a foreign country must be filed within 16 months of such a "priority" home country application or four months from the actual US patent application filing date.  This requirement is a big change from the recent requirement only that a "priority" claim be submitted in writing with the PTO without the actual submission of a certified copy of a priority document from a foreign patent office  being required until the end of the patent application review process, i.e.,  before the grant of the patent.  

The US Patent Office has certain procedures which allows  transfers of these documents to be done electronically; however as documented by others,  this process is particularly confusing and unreliable.  A patent applicant is thus advised to obtain a physical copy of the certified priority document from a foreign patent office for submission to the US Patent Office as soon as possible. The loss of a priority claim to a foreign patent application due to the lack of a timely submission of a certified copy of the priority document could cost $1700 to correct -assuming that such mistake is caught early enough.

The moral of the story for foreign applicants is to make sure that all ducks are in a row at the time of the filing of a US patent application, and in particular that a certified copy of an earlier home country foreign application be obtained from the foreign patent office and sent to the US Patent Office as soon as possible.