Note: This advice is given by the CAP Executive about non-broadcast advertising. It does not constitute legal advice. It does not bind CAP, CAP advisory panels or the Advertising Standards Authority.

Code rule 3.7 states that “before distributing or submitting a marketing communication for publication, marketers must hold documentary evidence to prove claims that consumers are likely to regard as objective and that are capable of objective substantiation. The ASA may regard claims as misleading in the absence of adequate substantiation”. Marketers should not make claims that consumers are likely to regard as objective unless they hold evidence to substantiate those claims.

Does the claim require substantiation? 
What evidence is needed?
Can testimonials be used as evidence?
What about comparisons?
What about claims for health and beauty products?
Are there any exceptions?

Does the claim require substantiation?

If consumers are likely to understand a claim as an objective one, capable of objective substantiation, then the marketer will be required to hold adequate supporting evidence (Code rule 3.7). Examples of objective claims include price statements (Simba Sleep Ltd, 21 Sept 2022, and Pelham Health Ltd, 09 Nov 2022) details about a product or service (Argos Ltd, 12 Oct 2022), and claims about the benefits or effects of using a product or service (THE PACK PET Limited, 02 Nov 2022 and Lakeland Paints, 14 Oct 2020).

The ASA will consider the likely interpretation of a claim, rather than the marketer’s intention. If the ASA considers a claim to be objective, they are likely to rule the claim misleading in the absence of adequate substantiation, even if the marketer’s intention was to make a subjective claim, or “puffery”.  The ASA considered the claim “the perfect network” to be an objective one in the context of the ad, despite the advertiser’s argument that it would be seen as puffery.  The ASA considered that, in the context of the claim being used in reference to the “network”, without qualification, consumers would understand it to be an objective claim that Sky Mobile performed to a very high standard across a range of factors related to their network. Additionally, because the ads claimed that Sky Mobile was “the perfect network”, consumers would understand the claim to mean that Sky Mobile was the only network which could be described as “perfect” (Sky UK Ltd, 8 June 2022). Similarly, the ASA considered the claim “best available tickets”. Whilst they appreciated that what was considered ‘best’ may have depended on individual preferences, they considered consumers were likely to view the claim to mean that those tickets offered a tangible benefit compared to other tickets , because, for example, they were closer to, or offered a better view of, the stage (Ticketmaster UK Ltd, 03 January 2018).

See Types of claims: puffery, Matters of opinion and Types of claims: general for more guidance on how to distinguish between objective claims and puffery.

What evidence do I need?

The type of evidence required will depend on the product or service, the level of claim concerned and the context in which it appears. 

Objective claims must be supported by objective evidence; self-reported consumer data or other subjective data will not be sufficient to support a claim that would otherwise require objective substantiation (see Substantiation: consumer surveys and sample claims).

Comparative claims are likely to require evidence which relates to all competitors which are being compared in the claim (see section on comparative claims below).

Efficacy claims made about health and beauty products, weight control products, food supplements and cosmetics are subject to additional sector specific rules. See Substantiation for health, beauty and slimming claims and CAP’s Advertising Guidance on this topic, for detailed guidance on the type of evidence the ASA is likely to expect marketers to hold.

See CAP Advertising Guidance – misleading environmental claims and social responsibility for advice on making environmental claims.

For advice on substantiating specific types of claims such as “best”, “best-selling” and “leading” see Types of claims: general.

Can testimonials be used as evidence?

Provided they are genuine, marketers may feature customer testimonials in their advertising, but these alone are unlikely to be considered sufficient to substantiate objective claims. Testimonials must relate to the product advertised and claims in a testimonial that are likely to be interpreted as factual must not mislead or be likely to mislead the consumer (Rules 3.46 and 3.47). Any objective claims made in testimonials, such as those about the efficacy of a product, must be supported by sufficient objective evidence to support the claim.

In February 2015, an advertiser submitted testimonials in support of efficacy claims for a copper bracelet in the treatment of restless leg syndrome and the ASA ruled that personal or customer endorsement alone did not constitute adequate substantiation (Halcyon Bracelets, 18 February 2015).

See Claims in testimonials and endorsements.

What about comparisons?

Comparisons can be both implicit and explicit and relate to both identifiable and non-identifiable competitors. Specific Code rules apply to ads which make comparisons (rules 3.33 – 3.38).

Marketers wanting to make objective comparisons, such as “leading”, “best”, or “cheaper”, must hold evidence relating to both their own products and those of the competitor or competitors that are the subject of the comparison.

When making comparisons with identifiable competitors, in addition to holding evidence to substantiate the claim, marketers must "compare products meeting the same need or intended for the same purpose" (3.34), and must "objectively compare one or more material, relevant, verifiable and representative feature of those products, which may include price" (3.35).

The ASA considered that the claim “The Best Alarm Technology on the Market” would be understood to mean that the advertiser’s alarm systems were technologically superior to all other providers in the UK. Because the advertiser only had evidence relating to three competitors, and a relatively small number of features offered, this was not considered adequate to substantiate the claim. (Verisure Services (UK) Ltd, 01 June 2022).

For detailed advice on the requirements when making comparisons see Comparisons: generalComparisons: identifiable competitors, and Types of Claims: general.

What about claims for health and beauty products?

Medical and scientific claims made about health and beauty products, including weight control products, food supplements and cosmetics, should be backed by evidence, where relevant consisting of trials conducted on human subjects (see rule 12.1 (health and beauty products and therapies), 15.7 (vitamins, minerals and other food supplements), 12.22 (cosmetics), 12.23 (hair and scalp) and 13.1 (slimming).

Marketers of health and beauty products wanting to make breakthrough claims about a product or treatment will need to hold a high level of robust evidence and should collate sound data to form a body of evidence. See Substantiation for health, beauty and slimming claims and CAP’s Advertising Guidance on this topic, for detailed guidance on the type of evidence the ASA is likely to expect marketers to hold.

Are there any exceptions?

While claims capable of objective substantiation will require supporting evidence, obvious exaggerations (“puffery”), and claims that the average consumer is unlikely to take literally are allowed, provided they do not materially mislead (rule 3.2).

Claims which are obviously a marketer’s subjective opinion and are unlikely to be interpreted as objective claims will not usually require supporting evidence, provided it is clear that marketers are expressing their opinion, rather than stating a fact (rule 3.6). In 2020 The ASA considered that the claim “THE BEST SINCE 2004”, in an ad for a pillowcase would be understood as a subjective expression of Slipsilk’s opinion about their product and was therefore not capable of objective substantiation (Slipsilk, 11 March 2020). Similarly, the claim "The most comfortable beds in the world", was considered subjective, given the experienced comfort of mattress types would vary between consumers (Hypnos Ltd, 26 November 2014).

See Matters of opinion, Types of claims: puffery, and Misleading advertising.

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