How does the USPTO evaluate “reasonable diligence” in filing a reissue application?

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 USPTO evaluates “reasonable diligence” in filing a reissue application on a case-by-case basis, considering the specific circumstances of each situation. According to MPEP 1403:

“What constitutes reasonable diligence must be determined on a case-by-case basis, taking all the facts and circumstances into account.”

Factors that the USPTO may consider include:

• The complexity of the subject matter
• The amount of time needed for research and preparation
• Any unavoidable delays (e.g., illness, natural disasters)
• Evidence of continuous effort towards filing
• The overall length of the delay

Applicants should document their efforts and be prepared to explain any periods of apparent inactivity to demonstrate reasonable diligence.