Website claims and the CAP Code: what UK firms can say

Key takeaways

Marketing claims on your own website are covered by the UK Code of Non-broadcast Advertising (CAP Code), enforced by the Advertising Standards Authority (ASA). You must hold evidence for objective claims before you publish them. Claims like 'best', 'cheapest' or 'number one' need proof. Specific, provable claims are both safer and more credible.

• The CAP Code covers marketing claims on businesses' own websites.
• You must hold evidence before making an objective claim.
• 'Best', 'cheapest' and 'leading' need proof unless clearly puffery.
• Specific, provable claims are safer and more persuasive.

Does the CAP Code apply to my website?

Yes. Since 2011 the ASA's remit has covered marketing communications on businesses' own websites and social media accounts, not only paid adverts. Claims about your products, services, prices and results on your website must not mislead, and objective claims must be substantiated. Editorial content, such as genuine articles, is treated differently from sales copy.

• How website design influences brand credibility
• ASA rules for social media advertising in the UK

What evidence do you need?

Rule 3.7 of the CAP Code requires marketers to hold documentary evidence to prove objective claims before publishing them. The ASA's substantiation guidance says the evidence must match the claim exactly. A claim of '98% customer satisfaction' needs a survey that measured that; 'trusted by 500 businesses' needs a client list.

• Numbers: the data, its date and how it was collected.
• Comparisons: like-for-like evidence about named or implied competitors.
• 'Best' or 'number one': independent evidence, unless clearly subjective.
• Results: typical outcomes, not only the best case.

• Cite your sources: back up the numbers on your website
• Why specific claims convert better than adjectives

How do you word claims credibly?

Replace superlatives with specifics. 'The best plumber in Leeds' is hard to prove and easy to doubt. 'Gas Safe registered, 412 five-star Google reviews, average arrival within 2 hours in LS postcodes' is provable and more persuasive. Date your figures and say where they came from.

• Accreditation badges on your website: which to show
• Showing Google reviews on your website, the right way

What about reviews and testimonials?

Testimonials must be genuine, held on file and reflect typical experience if presented that way. Since April 2025, the Digital Markets, Competition and Consumers Act 2024 also bans fake reviews and concealed incentivised reviews outright. Do not edit reviews in ways that change their meaning.

• Fake reviews law in the UK: what businesses must know
• Testimonials and case studies on your website

When is a claim just puffery?

The ASA accepts obvious subjective exaggeration that consumers would not take literally, known as puffery, such as 'the tastiest pies in town'. The line is whether a reasonable consumer would read it as an objective claim. When in doubt, either prove it or rephrase it as an opinion your customers express.

• Dark patterns: conversion tricks that break UK law

What does this look like in practice?

A pattern we see: a homepage says 'the UK's leading provider' because a previous agency wrote it. Nobody can say what it is based on. Replacing it with the number of clients served and a named accreditation removes the risk and gives visitors something they can check.

• See client work
• Website Design & Development for UK businesses

Website claims checklist

• List every objective claim on the site.
• Find and file the evidence for each one.
• Rewrite or remove any you cannot prove.
• Date your figures and name the source.
• Check reviews and testimonials are genuine and unedited.

• The website credibility score: rate your site out of 10
• Legal requirements for a UK business website

Next step

Search your site for 'best', 'leading', 'number one' and '%'. Each result needs evidence or a rewrite.