What is considered ‘proof of unavailability’ for a non-signing inventor?

Proof of unavailability for a non-signing inventor can include various forms of evidence. According to MPEP 409.03(d):

In the case of unavailability, proof of the inability to find or reach the non-signing inventor after diligent effort must be submitted.

This proof may include:

• Returned correspondence
• Copies of email or other communication attempts
• Statements from people with knowledge of the inventor’s unavailability
• Documentation of searches or inquiries made to locate the inventor

The key is to demonstrate a diligent effort to locate and communicate with the non-signing inventor.

To learn more:

• inventor unavailability
• proof of unavailability
• non-signing inventor
• diligent effort