What is the significance of the six-month period between effective filing dates in interference cases?

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 six-month period between effective filing dates plays a crucial role in determining how to proceed with potentially interfering applications. According to MPEP 2303.01:

“If the applications have their earliest effective filing dates within six months of each other, then an interference may be suggested.“

This six-month window is used as a threshold for deciding whether to initiate an interference proceeding or to allow the earlier-filed application to issue. When the filing dates are within six months of each other, it suggests that the inventions were likely developed around the same time, justifying a more detailed examination of priority through an interference proceeding.

On the other hand, if the filing dates are more than six months apart, the earlier-filed application is generally allowed to issue, potentially serving as prior art against the later-filed application or requiring a priority showing from the later applicant.