What is the “on sale” bar in patent law?

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 “on sale” bar in patent law refers to a provision that can prevent an inventor from obtaining a patent if their invention was on sale before the critical date. According to MPEP 2133.03(b):

“A sale is a contract between parties to give and to pass rights of property for consideration which the buyer pays or promises to pay the seller for the thing bought or sold.”

This bar is designed to prevent inventors from commercially exploiting their invention for an extended period before seeking patent protection.