Federal Circuit Clarifies Algorithm Disclosure Requirements for Means-Plus-Function Claims

April 9, 2012

Daniel T. Wehner PhD

What This Means To You

  • Describe disclosed algorithms corresponding to means- plus- function claims in as much detail as possible.
  • Write at least some apparatus claims without means-plus-function triggering language.


In a decision dealing with computer-implemented means-plus-function claims, the US Court of Appeals for the Federal Circuit (Federal Circuit) in Noah Systems v. Intuit held the disclosed algorithm must enable all recited functionality in the claim.

Case Background

Noah Systems sued Intuit alleging infringement of a patent related to an automated financial accounting system. Although both parties agreed that the operative claim language should be interpreted as a means plus function limitation, they disputed which disclosed structure in the specification performs the claimed function.

Decision Analysis

In citing prior decisions, the Federal Circuit stated that computer-implemented means-plus-function claims must “disclose an algorithm for performing the claimed function.”

In this case, the claim limitation at issue recited two distinct functions. Noah argued that a flowchart provided in the application was sufficient to support this limitation. The Federal Circuit disagreed, stating that the flowchart did not disclose an algorithm for one of the two functions in the disputed limitation and that this partial disclosure rendered the claim invalid as indefinite.


When drafting claims for computer-implemented inventions, we recommend including at least some claims that do not use claim language likely to be interpreted as indefinite under the means-plus-function section of the federal statute, as such claims will not be susceptible to the indefiniteness analysis presented in this case.

Do not assume that including a flowchart will be sufficient disclosure as each claimed function must be described.

For those accused of infringing a patent containing claims that may be interpreted as including means-plus-function language, this decision provides a framework for invalidating such claims as indefinite based on the sufficiency of the disclosed algorithm in the specification.