On-Sale Bar: 6 Rules to Avoid Losing Your Patent

You can lose a patent before you file it — not because someone beat you to the invention, but because you sold it too soon. The on-sale bar is one of the quietest ways strong inventions become unpatentable: a single commercial offer, even a confidential one, can start a one-year clock that ends in a forfeited right. This guide explains what the on-sale bar is under 35 U.S.C. § 102, how Pfaff and Helsinn define it, why secret sales still count, and six rules to keep an early deal from costing you the patent.

What the On-Sale Bar Means Under 35 U.S.C. § 102

The on-sale bar is a rule of novelty. Under 35 U.S.C. § 102(a)(1), an invention that was “on sale” before the effective filing date of your application cannot be patented. The America Invents Act (AIA) softens that with one escape hatch in § 102(b)(1): a sale traceable to the inventor is forgiven if the application is filed within one year. Miss that window and the sale becomes prior art against your own patent.

The purpose is to stop inventors from commercially exploiting an invention for years and then claiming a fresh 20-year monopoly on top of it. The bar is unforgiving because it does not care about intent. There is no “I did not realize” defense, no requirement that the sale be public, and no need for the buyer to understand the technology. If the invention was the subject of a qualifying commercial sale or offer more than a year before filing, the patent is invalid — full stop.

The Pfaff Two-Prong Test: Offer and Ready for Patenting

For decades courts argued over what “on sale” actually required. The Supreme Court settled it in Pfaff v. Wells Electronics, Inc., 525 U.S. 55 (1998), with a two-part test that still governs today:

1. A commercial offer for sale. The invention must be the subject of a real commercial offer — something the other side could accept to form a binding contract. Marketing puffery and early feelers usually do not qualify; a firm price quote or purchase order does.
2. Ready for patenting. The invention must be ready for patenting, shown either by an actual reduction to practice (a working version) or by drawings and descriptions detailed enough that a skilled person could build it.

Both prongs must be met on the same date for the clock to start. That matters in practice: an offer made before the invention is ready for patenting does not trigger the bar, and a finished invention that is never offered for sale does not either. The trap is that both conditions are often satisfied earlier than founders assume — a detailed quote to a first customer, sent while a tested prototype sits on the bench, can start the year running without anyone noticing.

Helsinn v. Teva: Even Secret Sales Trigger the Bar

Many inventors assume a confidentiality agreement keeps a deal from counting. It does not. In Helsinn Healthcare S.A. v. Teva Pharmaceuticals USA, Inc., 139 S. Ct. 628 (2019), the Supreme Court held unanimously that a sale can trigger the on-sale bar even when the terms of the invention are kept secret from the public.

Helsinn had entered a supply-and-distribution agreement for its drug and announced the deal, but kept the dosage — the patented feature — confidential. The Court held the AIA did not change the settled meaning of “on sale.” The catch-all phrase “or otherwise available to the public” did not add a public-disclosure requirement to sales. A commercial sale to a third party, even under an NDA, still counts.

The lesson is blunt: secrecy protects your technical details, not your filing deadline. If money changed hands or a binding offer was made for the invention, the one-year clock is likely running whether or not the world ever learns what you sold.

The One-Year Grace Period and Its Limits

The AIA grace period in § 102(b)(1) gives you twelve months from your own qualifying sale or disclosure to file. Used deliberately, it is a safety net. Relied on by accident, it is a countdown you never see. Three limits catch people off guard:

• It runs from the first triggering event. The clock starts on the earliest qualifying offer, not the last. A quiet quote in January is not reset by a splashy launch in June.
• It is a U.S. rule. Most of the world — including the EPO — applies absolute novelty with no general grace period. A sale that is merely late for the USPTO can permanently bar you abroad. See our guide to the patent grace period for the jurisdictional traps.
• It only forgives the inventor’s own activity. A third party’s independent sale of the same invention is prior art the grace period will not erase.

Treat the grace period as an emergency backstop, not a plan. The safest posture is to file — at least a provisional patent application — before any commercial offer goes out.

The Experimental Use Exception

Not every pre-filing activity is a “sale.” Genuine experimentation to perfect the invention is not commercialization, and it does not start the clock. The classic authority is City of Elizabeth v. American Nicholson Pavement Co., 97 U.S. 126 (1877), where an inventor tested a new wooden pavement on a public toll road for six years. Because the use was bona fide testing under his control, the Supreme Court held it did not bar the patent.

Courts look at whether the activity was truly experimental: Did the inventor keep control and monitor performance? Were records kept? Was the purpose to test the invention rather than to profit from it? Charging money, ceding control, or testing features unrelated to the claims all push an activity from “experiment” toward “sale.” The exception is real but narrow, and the inventor carries the burden of proving it — so document everything and never let a market test masquerade as an experiment.

6 Rules to Avoid Triggering the On-Sale Bar

Avoiding the on-sale bar is mostly about sequencing and record-keeping. These six rules keep an early commercial move from erasing your rights:

1. File before you sell. Get at least a provisional on file before any commercial offer, price quote, or purchase order leaves the building. Filing first makes the bar irrelevant.
2. Do not trust the NDA to save you. After Helsinn, a confidential sale still counts. Use NDAs to protect secrets, not to buy patent time.
3. Watch supplier and manufacturing deals. A supplier’s offer to make and sell your product to you can be a triggering sale, as in Hamilton Beach Brands v. Sunbeam Products, 726 F.3d 1370 (Fed. Cir. 2013). Sign the development contract, then file promptly.
4. Log the first-offer date. Track the earliest commercial offer for every product. That single date, not your launch, is where the one-year clock starts.
5. Keep experiments experimental. If you must field-test, retain control, keep records, avoid charging for the invention, and tie the testing to the claimed features.
6. Mind foreign filing. If you may want patents abroad, remember most countries offer no grace period. File before any public or commercial activity to preserve those rights.

The on-sale bar rewards discipline and punishes improvisation. When a challenger wants to knock out a patent, an early sale is one of the first things a prior art search for invalidation looks for — and a well-run freedom to operate search can surface a competitor’s own on-sale problems. Get the filing done before the deal, and you take the cheapest invalidity ground off the table before it exists.

How PerspireIP Can Help

PerspireIP helps inventors and counsel file before an early deal becomes an on-sale problem — and pressure-tests granted patents for on-sale and public-use weaknesses when you need to challenge one. Whether you are racing a launch or building an invalidity case, we map the timeline and the prior art. Contact us to protect your filing date before you sell.

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