How does the effective filing date affect the prior art in pre-AIA patent applications?

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 of a claimed invention in a pre-AIA patent application is crucial for determining what qualifies as prior art. According to MPEP 2139.01:

“The effective filing date of a claimed invention is important to determine because the effective filing date is the date that is used to determine which prior art is applicable to the claimed invention.”

This means that only prior art that predates the effective filing date can be used to reject the claimed invention. Understanding the effective filing date is essential for both patent examiners and applicants in assessing patentability.