Can we file a patent application in Japan with specification, claims, drawings, and abstract prepared in English?
Although the application per se has to be prepared in Japanese, the application can be filed with specification, claims, drawings, and abstract attached thereto prepared in English (JPL 36-2(1)).
In this case, a Japanese translation thereof must be filed within 1 year and 2 months from the earliest priority date (JPL 36-2(2), JPL 17-3).
The benefit of filing an application with English specification, claims, drawings, and abstract is not limited to the ease of filing an application in Japan claiming priority. By filing so, an amendment based on those English specification, claims, and drawings is allowable, which otherwise would not serve as a basis for amendment. This benefit becomes significant when translation errors are found.