Patent Disclosure Requirements

Best Mode Requirement

What inventors must disclose — and what changes post-AIA.

Quick Answer

35 U.S.C. § 112(a) requires inventors to disclose the best mode they know for carrying out the invention at filing. Post-AIA (2012), best mode failure no longer invalidates an issued patent in civil litigation — but it can still affect prosecution and pre-AIA patents remain fully vulnerable.

The Test

Two-Prong Best Mode Analysis

Best mode invalidity analysis uses a two-prong test established in Chemcast Corp. v. Arco Industries Corp. (Fed. Cir. 1991):

Prong 1 — Subjective

Did the inventor contemplate a best mode?

Entirely subjective — what did THIS inventor believe was the best way to practice the invention at filing? Measured by inventor's actual knowledge, not what a POSITA would think. An inventor with no preference among equally good alternatives satisfies Prong 1 (nothing to disclose). An inventor who clearly prefers one embodiment over others must disclose it.

Prong 2 — Objective

Was the best mode adequately disclosed?

Objective inquiry — would a person skilled in the art, reading the specification, be able to identify and practice the preferred embodiment? Disclosure need not use the label 'best mode' but must contain sufficient detail. Hiding specific preferred parameters, temperature ranges, materials, suppliers, or techniques while disclosing only generic alternatives is problematic.

AIA Reform

The AIA's Enforcement Change (2012)

The America Invents Act (AIA) significantly limited the best mode requirement's teeth in civil litigation. 35 U.S.C. § 282(b)(3)(A) now provides:

"The failure to disclose the best mode shall not be a basis on which any claim of a patent may be canceled or held invalid or otherwise unenforceable" in a civil action.

This applies to civil actions filed on or after September 16, 2012. The best mode requirement was retained in § 112(a) — the USPTO still examines for it, and PTAB can address it in post-grant proceedings — but a defendant in a patent infringement suit can no longer use best mode non-disclosure as an invalidity defense.

For pre-AIA patents (effective filing date before March 16, 2013), the old § 112 ¶ 1 applied and best mode remains a viable invalidity defense in litigation. Many high-value pharmaceutical, semiconductor, and chemical patents have pre-AIA effective dates — confirm before dismissing the defense.

Violation Patterns

How Best Mode Is Violated

Hidden preferred supplier

Inventor knows a specific commercial grade resin from a single supplier performs significantly better but claims only 'thermoplastic resin' generically. The spec never mentions the preferred supplier, trade name, or grade.

Withheld preferred parameters

Software patent where the inventor has a specific algorithm parameter (e.g., threshold value, learning rate) that produces optimal results but the spec only discloses a broad range without the preferred value.

Generic disclosure of preferred process

Chemical process patent where the inventor's preferred catalyst loading and reaction temperature are narrowed to specific values in internal testing but the spec claims a broad range to conceal the preference.

Trade secret encapsulation

Inventor deliberately writes claims broadly and references a trade secret-protected process in the specification without disclosure, effectively using the patent to monopolize the space while keeping the actual best method secret.

Context

§ 112(a) Requirements — All Four

35 U.S.C. § 112(a) contains four distinct disclosure requirements in a single sentence. Best mode is the last and most controversial:

Written Description

Specification must show inventor 'possessed' the claimed invention at filing. Measured by whether the spec 'conveys with reasonable clarity' possession — Ariad Pharm. (Fed. Cir. 2010).

Enablement

Spec must teach a POSITA how to make AND use the full scope of the claims without undue experimentation. Post-Amgen v. Sanofi (S.Ct. 2023), genus claims require enabled access to the full scope.

Written Description (Definiteness)

Claims must be 'definite' — inform a POSITA, with reasonable certainty, of the scope. Nautilus, Inc. v. Biosig Instruments (S.Ct. 2014) standard.

Best Mode

Inventor must disclose the best mode contemplated for carrying out the invention at filing. Subjective + objective two-prong test. Post-AIA: not an invalidity defense in civil litigation.

FAQ

What is the best mode requirement in patent law?

35 U.S.C. § 112(a) requires that the inventor disclose the best mode contemplated by the inventor for carrying out the invention at the time the application is filed. It's a two-prong test: (1) did the inventor subjectively contemplate a best mode? and (2) was that best mode adequately disclosed in the specification? The requirement is personal to the inventor — measured by the inventor's own subjective knowledge and preferences.

Can a patent be invalidated for failing to disclose the best mode after the AIA?

Post-AIA (effective September 16, 2012), failure to disclose the best mode can no longer be used as a ground for invalidity or unenforceability in a civil action (35 U.S.C. § 282(b)(3)(A)). Best mode non-disclosure can still be raised in USPTO post-grant proceedings and during prosecution. For applications filed before the AIA, the old pre-AIA § 112 applied and best mode was a viable invalidity defense.

What must the specification say to satisfy best mode?

The specification must enable a person skilled in the art to practice the best mode — it need not label the best mode as such. Adequate disclosure means sufficient detail that a POSITA can identify and practice the preferred embodiment. Generic descriptions that hide the inventor's specific preferred parameters, suppliers, or techniques may be insufficient if the preference was material to practicing the invention.

Does the best mode requirement apply to information the inventor learns after filing?

No. The best mode requirement is measured at the filing date of the application. Information about improved modes or preferences developed after filing does not need to be disclosed in the original application. This is why continuation applications can be useful — a CIP can incorporate newly developed best mode information, getting a new filing date for that new matter.

How does best mode differ from written description and enablement?

Written description requires the specification show the inventor possessed the invention; enablement requires the spec teach a POSITA how to make and use the full scope of the claims without undue experimentation; best mode requires disclosure of the inventor's personal preference for carrying out the invention. They can overlap — a hidden best mode often also creates enablement problems for the undisclosed preferred method.