What is the difference between express and formal abandonment of a patent 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.

Express abandonment and formal abandonment are two ways to voluntarily abandon a patent application:

• Express abandonment is initiated by the applicant or their attorney/agent by filing a written declaration of abandonment.
• Formal abandonment occurs when the applicant fails to reply to an Office action within the set statutory period or shortened statutory period.

According to MPEP 711.01: “Express abandonment of the application may be accomplished by filing in the United States Patent and Trademark Office a written declaration of abandonment identifying the application.”