Similar to U.S. patent law, Taiwan's patent system allows use of means-plus-function or step-plus-function language for claim limitations. Paragraph 8, Article 18 of the Enforcement Rules of Taiwan Patent Act ("Enforcement Rules"), as amended and implemented on 1 July 2004, stipulates that "For an invention characterized in combining a plurality of technical features, the claims may be presented in means-plus-function or step-plus-function language. Whenever an interpretation of claims is made, it shall contain the structure, material or acts or equivalent scope thereof corresponding to the functions disclosed in the description of an invention." This is similar to the U.S. Patent Law, 35 U.S.C. 112, which provides that "An element in a claim for a combination may be expressed as a means or step for performing a specified function without the recital of structure, material, or acts in support thereof, and such claim shall be construed to cover the corresponding structure, material, or acts described in the specification and equivalents thereof."

In lawsuits for infringement of a patent containing means-plus-function or step-plus-function claim limitations, the accused infringer (defendant) occasionally would employ the above principle provided in the Enforcement Rules (specifically, "Whenever an interpretation of claims is made, it shall contain the structure, material or acts or equivalent scope thereof corresponding to the functions disclosed in the description of an invention") to argue that the patent in question should be invalidated for not conforming to the "definiteness" requirement under Paragraph 2, Article 26 of the Taiwan Patent Act, which reads, "The description of invention shall contain a sufficiently clear and complete disclosure of contents of the invention so as to enable persons skilled in the art to understand the contents thereof and to practice said invention." This view prevailed in a decision rendered in January 2010 (Judgment No. 2009-Min Juan Shan-19), in which the Intellectual Property Court (IP Court) held that Claim 6 of the patent in question failed to meet the definiteness requirement

In practice, it is common for patent applications for business method inventions or software-related inventions to employ means-plus-function or step-plus-function format in the drafted claims. This is because technical features of such inventions are difficult to describe in terms of concrete structures or materials thereof, in which case functional language may serve as a more expedient way to limit the claims. However, the above principle provided in the Enforcement Rules still applies to these inventions, even though business methods and software are fundamentally different from mechanical inventions, the technical features of which normally involve specific physical structures, materials or acts. Thus, from a technical perspective, careful deliberation is required as to what the "structure, materials or acts" of a business method invention or a software invention actually refer to. If the court simply employs the aforementioned standard and invalidates a patent due to a lack of definiteness on the ground that "the specification fails to recite any structures, materials or acts corresponding to the means-plus-function limitations in the claim," without carefully probing into the criteria for "definiteness" set forth in Paragraph 2, Article 26 of the Taiwan Patent Act (i.e., "whether persons skilled in the art could understand the contents of and practice said invention"), the credibility of the court may suffer if unduly superficial standards of relevance are applied given the nature of the patent in question.

In the aforementioned 2010 case (Judgment No. 2009-Min Juan Shan-19), the patent in question, NI-152547, was entitled "System for automatically matching advertiser and advertising object and the matching method based on the same;" its Claim 6 reads, "A storage medium facilitating subscribers to automatically configure a desired advertising mode and category, which comprises: a functional means for configuring the advertisement mode, whereby allowing the subscriber to receive the feedback; a functional means for configuring advertisement category, whereby allowing the subscriber to configure the advertisement category desired to receive; a functional means for generating matching information; and a functional means for matching alert system, whereby allowing mutual matches with an advertising matching system." Although this claim is directed to a "storage medium," from the teaching of the specification, the substantial technical core thereof relates to a software invention, as asserted by the patentee (plaintiff) during the trial procedure. The IP Court ruled against the validity of the patent in question, after which the patentee appealed to the Supreme Court, which then reversed and remanded the IP Court's judgment on 31 March 2011, by Judgment No. 2011-Tai Shan-480.

The Supreme Court opined that the IP Court should investigate and clarify the type of claimed invention, and should not directly hold the patent "lacking definiteness" merely because no structure and material corresponding to the means-plus-function limitations of Claim 6 could be found in the specification or drawings.

On remand, the IP Court rendered a judgment No. 2011-Min Juang Shan Geng (1)-5 in October 2011, in which the IP Court still maintained its original position that "since there is no corresponding structure or material specified in the specification, Claim 6, having means-plus-function limitations, failed to comply with the requirement of definiteness." Moreover, the IP Court indicated that since the claimed objective of Claim 6 is not definitely specified, the court has no way to make any comparison between it and the prior art citations raised by the defendant to determine whether the claimed invention meets the requirements of novelty and inventive step.

It is worth mentioning that in the above 2011 case (Judgment No. 2011-Min Juang Shan Geng (1)-5), the IP Court cited U.S. law 35 U.S.C. 112, the "Supplementary Examination Guidelines for Determining Compliance with 35 U.S.C. 112 and for Treatment of Related Issues in Patent Applications" effective as of February 9, 2011 and cases such as In re Hayes Microcomputer Prods., Inc. Patent Litigation, 982 F.2d 1527, 1534 (Fed. Cir. 1992), Aristocrat Techs. Australia Pty Ltd. v. Int'l Game Tech., 521 F.3d 1328, 1333 (Fed. Cir. 2008), Finisar Corp. v. DirecTV Group, Inc., 523 F.3d 1323, 1340 (Fed. Cir. 2008) to support its view. The Court indicated that if the invention is software-related and the claim drafted with means-plus-function language, the patent applicant must describe in detail the algorithm of the software in the specification, so as to serve as a basis for the court or the patent authority to determine whether it has met the definiteness requirement. The IP Court stated that the domestic court can take such U.S. law and judgments as reference regarding legal principles.

It remains to be seen how the aforementioned opinion will influence practice on examination of software-related patents. Thus far, the Patent Examination Guidelines for software-related patents stipulate only that a flowchart or a function block diagram can be employed to illustrate the desired function of the software, and if necessary, data flow diagrams, pseudo codes, time charts, etc., can also be utilized to disclose the technical features, in order to enable persons skilled in the art to realize and implement the claimed invention accordingly. Once the IP Court's aforementioned opinion based on U.S. law regarding disclosure of the algorithm becomes a standard criteria for evaluating the definiteness of a means-plus-function claim of a software-related patent, further precedents will be needed to establish how the "algorithm" and its scope are defined, as well as how to correlate it to the "structure, material, and act" specified in the Enforcement Rules of the Taiwan Patent Act.

The aforementioned case was appealed again to the Supreme Court, decision pending.