Patent Invalidity · § 102(b)
The On-Sale Bar
Selling or offering to sell your invention before you file a patent application can permanently destroy your patent rights — even if the sale was confidential. The Pfaff two-part test determines when the bar applies.
The rule in plain English
If your invention was commercially offered for sale anywhere in the world more than one year before your US patent filing date, and it was ready for patenting at the time of the offer, the patent application will be barred — even if the sale was private or under NDA.
The statute
35 U.S.C. § 102(a)(1) — AIA version
“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.”
35 U.S.C. § 102(a)(1) (AIA, effective March 16, 2013)
The grace period under § 102(b)(1) carves out the inventor's own disclosures made within one year of filing. But after Helsinn Healthcare S.A. v. Teva Pharmaceuticals USA, Inc.(2019), the Supreme Court confirmed that secret sales still trigger the bar — the “otherwise available to the public” language did not eliminate secret-sale liability.
The controlling test
Pfaff v. Wells Electronics (1998) — two-part test
The Supreme Court's unanimous decision in Pfaff v. Wells Electronics established the definitive test for the on-sale bar. Both prongs must be satisfied for the bar to apply.
Key case
Helsinn Healthcare v. Teva (2019) — secret sales still bar
Helsinn Healthcare entered into a supply and purchase agreement with MGI Pharma in 2001 to supply a cancer drug (palonosetron) for reducing chemotherapy-induced nausea. The agreement was disclosed publicly but the actual drug dosage was kept confidential. Helsinn filed its patents in 2003 — more than one year after the supply agreement.
Teva argued the patents were invalid under the on-sale bar. Helsinn argued that the AIA's “or otherwise available to the public” language required the sale to be public for the bar to apply. The Supreme Court unanimously disagreed.
Helsinn's argument
AIA's 'otherwise available to the public' means all categories in § 102(a)(1) — including 'on sale' — must be public. A secret sale should no longer bar patentability.
Supreme Court held
Pre-AIA precedent treated secret sales as prior art. Congress is presumed not to change settled law without clear signal. 'On sale' still includes secret sales. Patents invalid.
Practical takeaway: An NDA does not protect you from the on-sale bar. Entering into any commercial agreement — manufacturing, supply, licensing to sell — triggers the one-year clock regardless of confidentiality provisions. File your patent application before signing any commercial deal.
The exception
Experimental use — the narrow exception
The experimental use doctrine, originating in City of Elizabeth v. American Nicholson Pavement Co.(1877), can negate the on-sale bar if the “sale” was for genuine experimental purposes — not commercial ones. Courts look at several factors:
Control retained
Did the inventor maintain control over the product during testing?
Compensation paid
Was payment received? Payment strongly suggests commercial, not experimental, purpose.
Confidentiality
Was the testing subject to confidentiality, or was it open to the public?
Duration
How long was the testing? Prolonged use weighs against experimental purpose.
Records kept
Were results systematically recorded? Experimental testing requires systematic data collection.
Purpose
Is the testing to determine whether the invention works, or to exploit a working invention commercially?
Warning: Experimental use is a narrow, fact-intensive exception. Courts are skeptical. The burden is on the inventor to prove the primary purpose was experimental, not commercial. The exception does not apply once the invention is known to work — testing after you know it functions is commercial, not experimental.
How to avoid the bar
File before you sell — always
File a provisional before any commercial discussion
Once you have a working invention described in enough detail, file a provisional patent application. The provisional costs $2,000–$4,000 with counsel and establishes a priority date. Any subsequent commercial discussions, offers, or sales will be within one year of your filing date — safely inside the grace period.
Treat your first purchase order as a hard deadline
As soon as you receive a purchase order, sign a supply agreement, or enter into any contract for the sale of the invention, the one-year clock starts. If you have not filed yet, you have one year from that date to file a non-provisional. Missing this deadline is fatal to US patent rights.
Audit contract manufacturing and R&D partnerships
If you outsource manufacturing or R&D, review every contract for commercial sale elements. A contract that gives the partner the right to sell units of your invention to end customers may trigger the on-sale bar, even if your company's name is not on the invoice.
Document experimental use carefully
If you must test your invention in the marketplace before filing, document everything: the experimental purpose, results recorded, control retained, absence of commercial terms. Courts require contemporaneous evidence — post-hoc explanations are rarely believed.
FAQ
On-sale bar questions
What is the on-sale bar in patent law?
The on-sale bar is a provision of 35 U.S.C. § 102(b) that prevents an inventor from obtaining a patent if the invention was on sale in the United States more than one year before the patent application's effective filing date. Under the AIA (post-March 16, 2013), the bar extends to sales anywhere in the world, not just in the United States. The bar is designed to prevent inventors from commercially exploiting an invention for more than one year before seeking patent protection.
What is the Pfaff two-part test for the on-sale bar?
In Pfaff v. Wells Electronics, Inc. (1998), the Supreme Court established a two-part test for the on-sale bar: (1) the product must be the subject of a commercial offer for sale — meaning a definite offer, not merely exploratory discussions or market research; and (2) the invention must be ready for patenting — meaning either the invention was reduced to practice, or the inventor had prepared drawings or descriptions sufficiently detailed to enable a person of ordinary skill to practice the invention. Both prongs must be met. A sale without a ready-for-patenting invention does not trigger the bar, and a ready-for-patenting invention with no commercial offer does not trigger the bar.
Does a confidential sale trigger the on-sale bar?
Yes — this is a critical trap. In Helsinn Healthcare S.A. v. Teva Pharmaceuticals USA, Inc. (2019), the Supreme Court held that a secret or confidential sale can trigger the on-sale bar under the AIA. Even if the details of the invention are kept confidential under an NDA, a commercial sale or offer for sale starts the clock. The AIA's addition of 'or otherwise available to the public' in § 102(a) did not change this rule — secret sales still trigger the bar. This means that a contract manufacturing agreement, a supply agreement, or a licensing deal that transfers the right to exploit the invention can all start the bar, even if they contain confidentiality provisions.
What does not count as an on-sale bar offer for sale?
Several activities do not constitute offers for sale that trigger the bar: (1) Internal testing or experimental use — use within the company for testing and development purposes is not a commercial offer; (2) Arm's-length experimental use — giving a product to a third party purely for experimental purposes, with no commercial transaction, can qualify as experimental use under the Manville line of cases; (3) Market research and customer interviews — asking potential customers if they would buy a product at what price is not an offer; (4) Patent licensing negotiations for the invention concept (not the product) may not trigger the bar; (5) A mere quote without the specificity of an offer under contract law principles may not qualify. The line between experimental use and commercial sale is fact-specific and often litigated.
How does the on-sale bar differ under pre-AIA and post-AIA law?
Under pre-AIA § 102(b), the on-sale bar applied to sales 'in this country' — US sales only. Under AIA § 102(a)(1) (effective March 16, 2013), the bar applies to sales 'anywhere in the world.' This means that a sale in Europe, China, or any other country now triggers the US on-sale bar under post-AIA law. Additionally, the one-year grace period under AIA § 102(b)(1) exempts your own disclosures from being prior art — but the Helsinn decision confirmed that the grace period does not apply differently to secret sales; secret sales by the inventor before the critical date can still trigger the bar. For patent applications with an effective filing date before March 16, 2013, the pre-AIA rules still apply.