Zink v. United States

The legal architecture governing the Research and Development (R&D) tax credit in the United States, codified under Internal Revenue Code (IRC), rests upon a foundation established by IRC. For over three decades, the Fifth Circuit’s decision in Zink v. United States, 929 F.2d 1015 (5th Cir. 1991), has served as the seminal authority for interpreting the "trade or business" requirement essential for qualifying research expenditures. This case articulated the "realistic prospect" test, a standard that differentiates bona fide innovative enterprises from passive investors seeking tax shelters. As the Internal Revenue Service (IRS) and the federal judiciary increasingly scrutinize R&D claims, the principles established in Zink have merged with modern interpretations of the four-part test for qualified research, creating a complex compliance landscape for taxpayers in the manufacturing, engineering, and technology sectors.

The Genesis of the Realistic Prospect Test: Zink v. United States

The controversy in Zink v. United States emerged during an era when partnerships frequently sought to leverage IRC  to deduct substantial research and experimental expenditures before a product ever reached the market. The taxpayers in Zink were partners in PCS Ltd., a partnership formed to develop specialized computer software and electronic hardware components. PCS Ltd. entered into a research and development agreement with a third-party firm, granting that firm the right to conduct the actual research while the partnership provided the capital.

The Fifth Circuit was tasked with determining whether these expenditures were incurred "in connection with" the partnership’s trade or business. While the Supreme Court in Snow v. Commissioner, 416 U.S. 500 (1974), had established that the  standard was broader than the "carrying on" requirement of, the Zink court clarified that this breadth did not extend to mere investors. The court held that to satisfy the trade or business requirement, a taxpayer must demonstrate a realistic prospect of subsequently entering its own business in connection with the fruits of the research, assuming that research is successful.

The failure of the Zink taxpayers was rooted in their lack of control and the contractual structure of their agreements. The court observed that the partnership had no realistic prospect of marketing the resulting software because it lacked the expertise, the personnel, and the capital necessary to bring the product to market independently. Furthermore, the research firm was granted an option to obtain an exclusive license to market the technology for a nominal sum (e.g., $5,000), suggesting that the partnership never intended to engage in the business itself but was merely financing a third party's innovation. This "passive investor" characterization has become a primary tool for the IRS to disallow credits for special-purpose entities and pre-revenue startups that outsource their entire research function without maintaining sufficient technical or commercial oversight.

Statutory Prerequisites: The Interplay Between Section 174 and Section 41

The implications of Zink are not confined to the deductibility of expenses; they are a prerequisite for the R&D tax credit itself. Under IRC, expenditures must first qualify as research and experimental costs under  to be eligible for the credit. Consequently, if a taxpayer fails the "realistic prospect" or "trade or business" test of, the  credit is automatically disallowed.

This relationship has become even more critical following the Tax Cuts and Jobs Act of 2017. For tax years beginning after December 31, 2021, IRC  requires the capitalization and amortization of research and experimental (R&E) expenditures over five years for domestic research and fifteen years for foreign research, rather than allowing an immediate deduction. This statutory shift has increased the financial impact of the trade or business determination, as the classification of an expense as "R&E" now triggers a mandatory amortization schedule while still serving as the gatekeeper for the dollar-for-dollar credit under.

Modern Judicial Reinforcement: From Investors to Active Participants

The "realistic prospect" test has been further refined by subsequent appellate rulings that have built upon the Zink foundation. In LDL Research Development II Ltd. v. Commissioner, 124 F.3d 1338 (10th Cir. 1997), the court denied deductions because the partnership lacked control over the research activities and had no plans to market the resulting technology should the research firm decline its purchase options. The Tenth Circuit emphasized that the partnership’s rights were purely "theoretic" and that the lack of manufacturing and marketing infrastructure rendered the activity a passive investment.

This distinction is critical for modern R&D service providers and their clients. If a service provider retains no rights and assumes no risk, the client is the taxpayer entitled to the credit. However, if the service provider retains substantial rights and bears the risk of failure, the research may be considered "funded" from the client's perspective, shifting the eligibility to the service provider. The Zink case informs the "Rights" side of this equation by establishing that a taxpayer must have more than a mere investment interest; they must have the legal right and practical ability to use the research in their own business.

The Documentation Imperative: Lessons from Recent Tax Court Jurisprudence

The most pervasive theme in modern R&D tax litigation is the failure of taxpayers to provide contemporaneous, activity-level documentation that substantiates the four-part test. The courts are increasingly moving away from accepting broad estimates or retrospective narratives in favor of a granular "scientific record" of the research process.

In Siemer Milling Company v. Commissioner (2019), the Tax Court disallowed over $235,000 in credits because the taxpayer failed to provide documentation linking specific employee activities to the resolution of technical uncertainties. Although the company was developing new flour products and experimenting with milling techniques, its records—such as undated project notes and vague wage summaries—were deemed insufficient to prove a systematic process of experimentation. The court specifically noted that conclusory statements about being involved in "technical activities" are not evidence of qualified research.

A similar outcome occurred in Phoenix Design Group, Inc. v. Commissioner (2024), where the court denied credits for structural engineering designs because the firm’s linear, six-stage design process did not constitute a "process of experimentation". The court found that performing routine calculations based on available data (e.g., determining duct size for airflow) is not an investigative activity if the information needed is already known or available through standard engineering principles. This ruling highlights a critical challenge for engineering firms: distinguishing "routine design" from "qualified research."

The Four-Part Test: Deep Dive into Experimentation and Uncertainty

The transition from the "discovery test" (which required a taxpayer to expand the "common knowledge" of a field) to the modern "process of experimentation" test has theoretically lowered the bar for technical innovation but raised the bar for procedural rigor. Under the current standard, research is qualified if it is undertaken to eliminate uncertainty regarding the capability, method, or appropriateness of a design, and substantially all of the activities constitute a process of experimentation.

The Elimination of Uncertainty

The uncertainty test requires that the information available to the taxpayer at the outset of the project must be insufficient to establish the final design. In Betz v. Commissioner, the court ruled that simply having design challenges is not the same as having technical uncertainty. The court rejected the taxpayer’s claim that post-production testing on air pollution control systems proved the existence of uncertainty, stating that conducting tests on a finished product does not prove that the "appropriate design as a whole remained uncertain" during the development phase.

Furthermore, the "discovery" of information must be technological in nature, meaning it must rely on principles of physical or biological sciences, engineering, or computer science. In several recent cases, the IRS has successfully argued that activities were actually "adaptation" (modifying an existing product for a specific customer’s need) or "routine engineering" rather than innovation.

The Process of Experimentation

The "process of experimentation" is the most litigated prong of the four-part test. It requires a systematic evaluation of alternatives through modeling, simulation, or iterative testing. The "substantially all" requirement dictates that at least 80% of the research activities must constitute elements of such a process. In Little Sandy Coal Co., Inc. v. Commissioner (2021), the court denied credits because the company failed to prove this 80% threshold.

The Phoenix Design Group decision is particularly instructive for the engineering industry. The court held that the firm’s work was "routine design" because it relied on standard calculations and historical data rather than hypothesis-driven testing. To qualify, a taxpayer must show they were "attempting to acquire information" that was not objectively available. If an engineer can solve a problem using a handbook or standard software without iterative evaluation of competing technical designs, the activity will likely fail the experimentation test.

The Funded Research Barrier: Rights, Risk, and Contractual Nuance

The "funded research" exclusion under IRC  prevents a taxpayer from claiming the credit for research that is funded by another person or entity through a grant, contract, or otherwise. To avoid this exclusion, a taxpayer must satisfy a two-prong test: they must bear the financial risk of failure and retain substantial rights to the research results.

Financial Risk and Contingent Payment

Research is considered funded if the taxpayer is entitled to payment regardless of the research’s success. In Meyer, Borgman & Johnson, Inc. v. Commissioner (2024), the Eighth Circuit upheld the denial of credits for a structural engineering firm because its contracts did not make payment contingent on the successful resolution of technical uncertainty. The firm argued that it had to meet building codes and design specifications to be paid, but the court found that standard quality assurance and inspection provisions do not create the "contingent on success" requirement necessary for the credit.

Conversely, System Technologies, Inc. v. Commissioner (2025) provided a significant victory for taxpayers. The court found that even though the contract was not explicitly "contingent," the existence of warranty provisions and the potential for a total breach under Indiana state law meant the taxpayer bore the financial risk. If the research failed, the client had legal remedies to recover payments, effectively placing the risk on the developer.

Retention of Substantial Rights

The "rights" prong requires the taxpayer to retain "substantial rights" to the research. In Smith et al. v. Commissioner (2025), the IRS argued that an architectural firm divested its rights by transferring design documents to its clients. However, the court ruled that "transfer of documents with shared rights alone does not divest the taxpayer of substantial rights". The court turned to local law (including foreign laws in Dubai and the UAE) to determine that IP rights often remain with the creator unless explicitly forfeited in the contract.

The "Shrinking-Back" Rule: A Strategic Compliance Tool

One of the most complex aspects of the R&D credit is the "shrinking-back" rule. If a taxpayer's entire business component (e.g., a whole building or a complete software suite) fails the four-part test, the rule allows the taxpayer to "shrink back" the analysis to a smaller subcomponent (e.g., a unique structural joint or a specific algorithm) to see if that specific part qualifies.

In Phoenix Design Group, the court noted the rule but could not apply it because the taxpayer’s record-keeping was so poor that it lacked the documentation to support eligibility even at the subcomponent level. This demonstrates that while the shrinking-back rule is a powerful defensive tool, it requires an even higher level of granular documentation to be successful. Taxpayers must be able to segregate the labor and supply costs associated with the innovative subcomponent from the routine costs of the overall project.

Procedural Challenges and Accuracy-Related Penalties

The IRS has signaled a more aggressive stance on R&D credit compliance, particularly regarding refund claims and the imposition of penalties. Under IRC, a 20% accuracy-related penalty can be imposed for "substantial understatement of income tax" or "negligence or disregard of rules".

In Betz v. Commissioner, the court upheld these penalties because the taxpayer failed to demonstrate they were exempt under the "reasonable cause and good faith" exception of. The taxpayer claimed they relied on professional advice, but the court found that this advice was not based on a proper analysis of the technical activities and contemporaneous records. Similarly, in Phoenix Design Group, the parties stipulated to the penalties if no qualified research was found in the sampled projects, a high-stakes agreement that underscores the risks of modern R&D audits.

Conversely, the Siemer Milling case highlights the "good faith" defense. While the court disallowed the credits due to poor documentation, it waived the penalties because the company had provided its accountants with full access to its records and acted reasonably in following their advice. This suggests that transparency and professional engagement can still serve as a shield against the most severe financial consequences of a denied claim.

Strategic Implications for Future R&D Tax Credit Applications

The synthesis of the Zink "realistic prospect" test and the modern technical requirements of  creates a roadmap for future R&D tax credit applications. The era of "after-the-fact" credit studies and broad estimations is giving way to a requirement for "R&D-aware" business operations.

Contractual Engineering for Funded Research Defense

To protect the ability to claim credits, companies must review and potentially rewrite their customer contracts. The Smith and System Technologies cases demonstrate that "contracts will not have to be written with the R&D Credit in mind to satisfy the requirements," provided that local law and general warranty provisions imply risk and rights. However, relying on judicial interpretation of local law is a high-risk strategy. Future applications are more likely to succeed if contracts explicitly state:

• That the developer retains a non-exclusive, perpetual right to use the technical knowledge and IP generated during the project.
• That payments are structured as milestones that are explicitly contingent upon the achievement of technical specifications or the successful resolution of design challenges.

Technical Documentation Protocols

Taxpayers must implement tracking systems that mirror the scientific method. This includes documenting the specific technical uncertainties at the "outset" of a project, rather than trying to identify them during an audit years later. Documentation should follow a narrative of "Hypothesis-Test-Evaluation-Iteration." Linear project management charts should be supplemented with technical logs that show alternative designs were considered and rejected based on performance data.

Managing the Section 174 Amortization Burden

With the post-2021 requirement to capitalize and amortize R&E expenditures, the classification of costs as "research" is no longer purely beneficial. Taxpayers must now balance the desire for a  credit with the tax burden of  amortization. This makes the "permitted purpose" and "uncertainty" tests even more critical; if an activity is "routine design" or "adaptation," it might be currently deductible as a  business expense, avoiding amortization but also sacrificing the credit. The "Zink" test remains the boundary; if there is no realistic prospect of a trade or business, the expenses are neither deductible nor amortizable as R&E, potentially leading to permanent loss of the tax benefit.

Conclusion: Synthesizing the New Compliance Standard

The legacy of Zink v. United States is a clear demarcation between the "investor" and the "entrepreneur" in the realm of tax-advantaged innovation. As the R&D credit has evolved, this distinction has shifted from a question of mere intent to a question of documented methodology. The recent string of Tax Court decisions—Betz, Siemer Milling, Meyer, and Phoenix Design Group—all point toward a single conclusion: the R&D tax credit is not an entitlement for technical complexity, but a reward for a documented process of experimentation conducted at the taxpayer's risk.

For future applications in the USA, the "Zink" realistic prospect test serves as the entry point, while the granular four-part test serves as the gauntlet. Success requires a multidisciplinary approach that integrates legal contract drafting, precise accounting for the shrinking-back rule, and a rigorous scientific approach to technical documentation. By understanding the causal relationships between contractual terms, risk allocation, and the iterative nature of experimentation, taxpayers can navigate the shifting sands of R&D tax law and preserve this vital lifeline for American innovation.