The word "substantiate" appears throughout Directive 2024/825/EU without being precisely defined. Article 3 of the directive requires that explicit environmental claims be based on "recognized scientific evidence" and "best available technical knowledge." Recital 19 clarifies that substantiation must account for the "life cycle of the product, the relevant environmental impacts, and the characteristics of the product or organisation." But the directive doesn't specify what documents count, what methodology is required, or what threshold of confidence is sufficient.

This ambiguity is frustrating from a compliance standpoint, but it's not arbitrary. The directive is designed to accommodate a range of claim types across many sectors, and a single substantiation standard would either be too prescriptive for some or too permissive for others. In practice, what "substantiated" means is determined by case law, regulatory guidance, and — ultimately — the judgment of the competent authority reviewing the claim.

Understanding how that judgment tends to be exercised is more useful than looking for a single definition.

The Starting Point: Is the Evidence Independent?

Regulators consistently weight independent evidence more heavily than internal evidence. A life cycle assessment conducted by an accredited third-party assessor, a certification audit by an approved certification body, or test results from an accredited laboratory carry more weight than internal analyses, supplier self-declarations, or brand-commissioned studies.

This doesn't mean internal evidence is worthless — it can be valuable as part of a substantiation package, especially where independent verification of every component isn't feasible. But where regulators have found substantiation insufficient, the consistent pattern is over-reliance on the brand's own assessment of its own claims.

The practical implication: the further removed the evidence is from the party making the claim, the more credible it is. Supplier self-declarations are less credible than supplier audits. Brand-internal LCAs are less credible than third-party LCAs. Trade association figures are less credible than published, peer-reviewed methodology.

The Scope Requirement

The evidence must cover the scope of the claim. This sounds obvious but is violated constantly.

A brand claiming "reduced environmental impact" needs evidence covering the impacts most relevant to the product category — for a textile product, that typically means fiber production, fabric processing, and garment manufacturing. If the evidence only covers one of those stages, it doesn't substantiate a claim about the product's environmental impact as a whole.

The ACM, in its 2024 guidance, proposed a useful test: if a reasonable consumer would interpret a claim as covering a broader scope than the evidence covers, the claim is misleading regardless of whether the evidence is accurate within its own scope. This is the scope test. It applies to both the categories of environmental impact covered and the parts of the supply chain covered.

The Specificity of the Claim Matters

The substantiation burden scales with the strength and breadth of the claim. A claim that "this garment uses 30% less water in dyeing than our previous production method" needs evidence for exactly that comparison — the water consumption figures for both processes, documented by comparable methodology. A claim that "this garment is made with recycled materials" needs documentation of the recycled content percentage and the supplier's ability to verify it.

The reason to be specific isn't just legal defensibility. Specific claims tend to be more credible to consumers than general ones — and more durable under regulatory scrutiny, because there's less room for interpretation about what the claim is asserting.

Claims that are simultaneously broad and hedged — "better for the environment," "a more responsible choice," "part of our sustainability journey" — are neither substantiated nor legally safer than specific claims. They're simply vague in a way that creates a misleading impression without making a falsifiable assertion.

What the Methodology Must Address

For claims that rest on a quantitative comparison or assessment, regulators look for:

A defined functional unit. What is being measured? For a garment, this might be one garment over its useful life, or one kilogram of finished textile. The functional unit defines what the numbers are about.

A defined system boundary. What stages of production are included in the assessment? Fiber production, fabric processing, garment manufacturing, use phase, end of life? The system boundary determines what the numbers cover, and a claim's scope should match it.

A specified reference scenario. If the claim is comparative, what is it being compared to? An industry average (which one, calculated how?), a previous product (measured when, how?), a virgin material alternative (which one)?

An applied methodology. Life cycle assessments should reference ISO 14040 and 14044, the internationally recognized frameworks. Carbon footprint calculations should reference the GHG Protocol or PAS 2060. Methodology transparency matters because it allows the figures to be independently checked.

None of this requires an LCA for every product claim. A claim about recycled content doesn't need a life cycle assessment — it needs supplier documentation of the recycled fiber percentage. But for any claim that goes beyond verifiable material facts into the territory of environmental impact assessment, the methodology needs to be there.

The Documentation Obligation

Under ECGT, economic operators must be able to provide the substantiation for their claims to the relevant competent authority upon request. This isn't a hypothetical requirement — several enforcement actions have begun with exactly this type of information request. If you can't produce the documentation, you can't demonstrate the claim is substantiated.

The documentation should exist before the claim is made, not be assembled after the claim is challenged. Substantiation is not a retrospective exercise. The evidence that supports a claim is what determines whether the claim was compliant when it was made — not what gets produced in response to an inquiry.

This is the practical argument for building a documentation system alongside your sustainability communications program. The moment to organize your evidence is when you're making the decision about what to claim, not after someone asks you to prove it.

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References: Directive 2024/825/EU, Articles 3 and 4; ISO 14040:2006 and ISO 14044:2006 (Life Cycle Assessment); GHG Protocol Product Standard; PAS 2060:2014 (Carbon Neutrality).