What is the “effectively filed” date for subject matter in a U.S. patent document?

This page is an FAQ based on guidance from the Manual of Patent Examining Procedure. It is provided as guidance, with links to the ground truth sources. This is information only: it is not legal advice.

The “effectively filed” date for subject matter in a U.S. patent document is crucial for determining its prior art status. According to MPEP 2154.01(b):

The “effectively filed” date of a subject matter described in a U.S. patent document … is the earlier of: (1) The actual filing date of the patent or the application for the patent containing the subject matter; or (2) The filing date of the earliest application to which the patent or application is entitled to claim a right of priority or benefit which describes the subject matter.

This means that the effectively filed date can be earlier than the actual filing date if the subject matter is supported by an earlier application in the priority chain.