What does a £56million VAT dispute teach us about instructing an expert witness?
A recent decision by the Upper Tribunal goes to the heart of my expertise as a food science expert and considers when expert evidence is “reasonably required” to resolve a VAT case.
HMRC v Healthspan Ltd [2026] UKUT 00194 (TCC) is instructive to both counsel and expert witness regarding the scope, relevant and correct legal test to apply when considering using a expert witness as part of the a case. In the following article I want to provide a brief overview of the key features of the case and how the outcome should be applied to the development of expert witness reports and related instruction.
The £56 million question!
The Healthspan Limited claimed a VAT refund of over £56 million on food supplements it argued were zero-rated as "food of a kind used for human consumption" under Schedule 8 to VATA 1994. HMRC disagreed. The dispute turned on what "food" means: HMRC argued for an "ordinary person" test, while Healthspan contended the definition should be based on nutritional purpose or content.
Healthspan applied to the First-tier Tribunal (FTT) for permission to adduce expert evidence on three topics:
The scientific understanding of food
The nutritional profile of the products
The extent to which the products fit with the modern diet
The FTT granted permission on all three limbs. HMRC appealed. The Upper Tribunal set aside the FTT's decision and remade it — allowing expert evidence only on the nutritional profile limb, and only in a narrowly defined way.
What went wrong with the FTT?
The Upper Tribunal found the FTT had applied the wrong test. The FTT had asked whether the evidence would be "in the interests of justice" and whether it would "assist the tribunal" if Healthspan's interpretation turned out to be correct. That's not enough.
The correct test, by analogy with CPR Part 35, is whether the evidence is "reasonably required to resolve the proceedings". This requires a structured, disciplined approach:
"The tribunal must consider whether the evidence is necessary, whether it will assist the tribunal on a pleaded factual issue, and whether it is reasonably required to resolve the proceedings in the context of the case as a whole."
The Upper Tribunal emphasised that this is not a tick-box exercise. You can't just say "it might help" or "it won't do any harm." You must show the evidence is necessary to decide a live issue that the tribunal cannot resolve without expert assistance.
Limb 1: The scientific understanding of food — refused
Healthspan wanted an expert to explain "the scientific understanding of food." The Upper Tribunal said no. The proposed evidence was too vague and general — it wasn't tied to any specific pleaded issue. The tribunal noted:
"The limb is opaque and not rooted in the pleadings. It is not clear what specific factual issue this evidence is intended to address."
The evidence also risked usurping the tribunal's role. Defining "food" for VAT purposes is a question of statutory interpretation — a matter for the tribunal, not an expert. Broad, unfocused expert evidence leads tribunals down rabbit holes that don't help resolve the actual dispute.
Practical lesson for instructing parties: Don't ask for expert evidence on general background topics unless you can show exactly how it addresses a specific factual issue the tribunal must decide. Vague, scene-setting evidence is unlikely to meet the "reasonably required" test.
Limb 2: Nutritional profile — allowed (but narrowly)
The Upper Tribunal allowed expert evidence on the nutritional profile of the products, but only in a tightly defined way. The expert could address:
The nutritional content of the products (vitamins, minerals, macronutrients, etc.)
The physiological function of those nutrients in the human body
Whether the products provide nutritional value
The expert could not opine on whether the products are "food" in law or whether they meet any legal test. Those are questions for the tribunal.
Why was this limb allowed? Because nutritional content was central to Healthspan's pleaded case. To assess Healthspan's argument, the tribunal needed to understand what nutritional value the products actually have — and that's a matter requiring scientific expertise. The Upper Tribunal noted that expert evidence on nutritional matters is not unprecedented in VAT food classification disputes, citing cases like Arthro Vite Ltd v HMCE (1996) and Telemara Limited v HMRC [2025] UKFTT 01123 (TC).
Practical lesson for experts: Stay in your lane. Your job is to provide the tribunal with the scientific or technical information it needs to decide the case. It's not your job to interpret the law or tell the tribunal what conclusion to reach. If you stray into legal territory, your evidence may be excluded — or worse, it may undermine your credibility.
This is a major issues “true expert witnesses” can face. You have specific obligations under CPR 35 but many clients will think and will try to push you to give and opinion on the classification of the product. This is not your role. Leave such issues to potentially untrained ‘lay witnesses’ who may make such mistakes. Where possible help your client understand the difference in your role and for them to ensure they deliver a clearly defined scope of work with relevant questions.
Those early in thirties expert witness careers may feel pressured to weigh on the side of the instructing party if they are the ones paying you. Don’t. You are there to provide an independent report and must do so to have longevity in this role.
Limb 3: Limb 3: Fit with the modern diet — refused
Healthspan wanted expert evidence on how the products "fit with the modern diet." The Upper Tribunal refused permission. The problems:
Lack of clarity: What is "the modern diet"? In a diverse society with different ages, cultures, and socio-economic groups, there is no single pattern of food consumption.
Not rooted in the pleadings: The connection between this evidence and Healthspan's pleaded case was unclear.
Risk of distraction: The evidence risked leading the tribunal into adjudicating on the contents of a "modern diet" without helping it decide whether the products qualify for zero-rating.
Duplication: It wasn't clear what this limb would add over and above the nutritional profile evidence.
“Practical lesson for instructing parties: Don't ask for expert evidence that's tangential to your pleaded case. If you can't explain clearly how the evidence addresses a specific issue the tribunal must decide, it's probably not "reasonably required."
The structured approach: a checklist for instructing parties
The Upper Tribunal set out a clear framework for deciding whether expert evidence should be admitted. If you're applying for permission to adduce expert evidence, ask yourself:
Is the evidence necessary? Can the tribunal decide the issue without it, using its own knowledge and experience?
Does it assist on a pleaded factual issue? Is there a specific factual question in dispute that the expert can help answer?
Is it reasonably required to resolve the proceedings? In the context of the case as a whole, is this evidence proportionate and genuinely needed?
If the answer to any of these questions is "no," your application is likely to fail.
The bottom line
The case has some gems of information in it as well as some concerns regarding the suggested us of more law witness as an option to experts. It’s key to remember law witnesses are not expert witness and their duties to the court are not the same.
The Healthspan case is a reminder that expert evidence is a tool, not a right. It's there to help the tribunal decide factual issues that require specialist knowledge — not to bolster a party's case with impressive-sounding background material, or to tell the tribunal how to interpret the law.
If you're instructing an expert, be disciplined. Define the scope of the evidence clearly. Tie it to your pleaded case. Make sure it's proportionate. And be prepared to explain why the tribunal can't decide the issue without it.
If you're an expert, stay in your lane. Answer the specific questions you're asked. Don't stray into legal interpretation. Make sure your report is focused, relevant, and grounded in your area of expertise.
The Upper Tribunal's decision is a masterclass in proportionate case management. It's also a warning: if you ask for too much, you may end up with nothing.
SOURCES
HMRC v Healthspan Ltd [2026] UKUT 00194 (TCC) —
https://caselaw.nationalarchives.gov.uk/ukut/tcc/2026/194
Arthro Vite Ltd v HMCE (1996) VAT Decision Number 14836
Telemara Limited v HMRC [2025] UKFTT 01123 (TC)
Bottled Science Ltd v HMRC (FTT)
Civil Procedure Rules Part 35 — https://www.justice.gov.uk/courts/procedure-rules/civil/rules/part35
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