(a) Novelty; Prior Art.— A person shall be entitled to a patent unless— (1) the claimed invention was patented, described in a printed publication, or in public use, on sale, or otherwise available to the public before the effective filing date of the claimed invention... An impermissible sale has occurred if there was a definite sale, or offer to sell, more than 1 year before the effective filing date of the U.S. application and the subject matter of the sale, or offer to sell, fully anticipated the claimed invention or would have rendered the claimed invention obvious by its addition to the prior art.
102(b) is triggered if the invention is both Traditional contract law principles are applied when determining whether a commercial offer for sale has occurred.
The on-sale bar is an extraordinarily (some would argue needlessly) complex body of patent law in all but the simplest cases.
The normal standard of reduction to practice (which requires recognizing the invention) has been ignored in several cases, for example an offer for sale of a waste disposal machine which, if accepted would have practiced a later invention due to the special nature of the waste, was considered a barring sale even though the invention had not even been conceived yet and the sale did not take place.
There is no joint-development exception to the on-sale bar, meaning that the on-sale bar in many cases is triggered when the invention is "ready for patenting," which can occur when an inventor is working alone at a drafting table.