Who Actually Invented It: Inventorship, Conception, and the Error That Voids a Patent
By Casey Scott McKay ·
Inventorship is determined claim by claim, it is a question of law with heavy factual underpinnings, and getting it wrong is one of the few remaining ways to render a patent unenforceable. This article explains what conception means, why reduction to practice is largely irrelevant to who is named, and how the joint inventorship test actually operates - including the collaboration requirement and the rule that contributions need not be equal or simultaneous. It works through the two most consequential consequences of error: correction under Section 256, which is now available for almost any good-faith mistake, and joint ownership, under which every co-owner may license the whole patent without accounting to the others. It covers the assignment gaps that turn an inventorship question into a standing problem, and closes with what diligence should ask.
IP and Technology > Patent Counseling Transactions | Article | Published 4 November 2025 - Updated 25 February 2026 | Casey Scott McKay - marksy.us
Summary. Inventorship is determined claim by claim, it is a question of law with heavy factual underpinnings, and getting it wrong is one of the few remaining ways to render a patent unenforceable. This article explains what conception means, why reduction to practice is largely irrelevant to who is named, and how the joint inventorship test actually operates — including the collaboration requirement and the rule that contributions need not be equal or simultaneous. It works through the two most consequential consequences of error: correction under Section 256, which is now available for almost any good-faith mistake, and joint ownership, under which every co-owner may license the whole patent without accounting to the others. It covers the assignment gaps that turn an inventorship question into a standing problem, and closes with what diligence should ask.
Keywords: inventorship · conception · definite and permanent idea · joint inventorship · Pannu factors · claim by claim analysis · reduction to practice · ordinary skill contribution · collaboration requirement · Dana-Farber · section 256 correction · deceptive intent removed · derivation proceedings · joint ownership consequences · each owner may license · assignment gaps · present assignment language · standing to sue · AI as inventor · diligence findings
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