How does delay in filing a patent application affect suppression or concealment?

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 delay in filing a patent application can potentially lead to an inference of suppression or concealment, especially in interference proceedings. However, the MPEP clarifies:

“Once an invention is actually reduced to practice an inventor need not rush to file a patent application. […] The length of time taken to file a patent application after an actual reduction to practice is generally of no consequence except in an interference proceeding.”

In interference proceedings, an unreasonably long delay between reduction to practice and filing can create an inference of suppression or concealment. However, this inference can be rebutted by showing diligence in preparing and filing the application. The reasonableness of the delay is determined on a case-by-case basis.