How is the effective filing date determined for claimed inventions?

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 effective filing date for a claimed invention is determined as follows:

• The actual filing date of the application containing the claim, or
• The filing date of the earliest application for which the patent or application is entitled to claim priority or benefit

The MPEP cites 35 U.S.C. 100(i)(1): “the effective filing date for a claimed invention in a patent or application (except in an application for reissue or reissued patent) is set forth in 35 U.S.C. 100(i)(1) as: (A) if subparagraph (B) does not apply, the actual filing date of the patent or the application for the patent containing a claim to the invention; or (B) the filing date of the earliest application for which the patent or application is entitled, as to such invention, to a right of priority under section 119, 365(a), 365(b), 386(a), or 386(b) or to the benefit of an earlier filing date under section 120, 121, 365(c), or 386(c).” (MPEP 210)