UK Advertising Rules for Small Businesses: The CAP Code in Plain English

By the Oski Marketing team · Updated 5 October 2026 · 6 min read

The CAP Code is the UK's rulebook for non-broadcast ads, including websites, social posts, leaflets and vans. For a small business the core rules are simple: do not mislead, hold proof for any factual claim before you publish it, show prices consumers will actually pay, use only genuine testimonials, and make ads obviously ads.

This is a general guide, not legal advice. Rule numbers below are from the CAP Code on the ASA website at the time of writing.

What is the CAP Code and who enforces it?

The CAP Code is written by the Committee of Advertising Practice and enforced by the Advertising Standards Authority (ASA). It covers non-broadcast marketing: online ads, your website, social media, email, posters, leaflets, van livery and so on. TV and radio have a separate code.

You do not need to read all of it. Most small business problems come from a handful of rules in Section 3 (misleading advertising) and Section 2 (making ads recognisable). The table below covers the ones we see owners trip over most.

What counts as a misleading claim?

Anything likely to give people the wrong impression about something that would affect their decision. That covers what you say, what you leave out, and how it looks. Rule 3.1 says marketing must not "materially mislead or be likely to do so", and rule 3.3 adds that leaving out material information can mislead too.

Common examples for local businesses:

• "Open 24/7" when calls after 10pm go to voicemail.
• "Local" when the work is subcontracted from another region.
• "From £49" when almost no job actually comes in at that price.
• Before and after photos that are not your work or have been edited.
• "Gas Safe registered" or "NICEIC approved" when the registration has lapsed.

What does "hold evidence" mean in practice?

Rule 3.7 says you must hold documentary evidence to prove claims that consumers are likely to see as objective, and you need it before the ad goes out, not after a complaint. Objective means measurable: speeds, prices, percentages, comparisons, "most", "fastest", "cheapest", "No.1".

A simple test: if a customer asked "says who?", could you show them a document? For a fictional dog groomer in Leyton claiming "the only groomer in E10 open on Sundays", the evidence would be a dated check of every other groomer's hours. If you cannot produce something like that, soften or drop the claim. Our separate guide on whether you can call your business "the best" covers superlatives in detail.

What are the rules on prices?

Prices must not mislead by omission, emphasis or distortion (rule 3.17), and quoted prices must include non-optional taxes, duties, fees and charges that apply to all or most buyers (rule 3.18). If a charge cannot be calculated in advance, rule 3.19 says you must make clear it is excluded.

For trades and services this means:

1. Show VAT-inclusive prices to consumers if you are VAT registered.
2. Include any fee everyone pays, such as a call-out charge, or state it clearly next to the price.
3. Only use "from" prices if a fair share of jobs really come in at that price.
4. If something is "free", make sure it really is: rules 3.23 and 3.24 limit what you can charge for a free offer.

How should you use reviews and testimonials?

Use them, because they are persuasive, but follow the testimonial rules. The ASA's testimonials guidance says you need evidence that testimonials are genuine and permission to use them (rule 3.50). Testimonials must relate to what you are advertising (rule 3.48) and must not include factual claims that would mislead (rule 3.49).

The ASA also points out in The facts about opinions in advertising that a testimonial cannot be used to make a claim you could not otherwise make. "Best plumber in London, fixed my boiler in ten minutes" from a happy customer is still a claim you would need to stand behind if you put it in an ad.

Can you offer a guarantee?

Yes, if it is real and its conditions are clear. The ASA's guarantees guidance says the word should not confuse consumers about their legal rights (rule 3.55), significant limitations must be stated clearly up front (rule 3.56), and money-back guarantees must be honoured promptly (rule 3.57).

A good guarantee for a fictional locksmith in Hackney might read: "If the lock we fit fails within 12 months through a fault in our workmanship, we will fix it free. Excludes damage and forced entry." Clear, specific and something the business can deliver.

How can you check an ad before it goes out?

Use the ASA's free Copy Advice service. The CAP Copy Advice team reviews draft ads in confidence, with a free standard turnaround of 3 to 5 working days. Paid fast-track options start at £150 including VAT for a 48-hour response. The advice is not binding, but it is a quick sense-check, especially for health, finance or comparison claims.

Before you send anything, run your own check:

• Is every factual claim backed by a document you could send today?
• Are prices complete, with VAT and unavoidable fees?
• Are testimonials genuine and used with permission?
• Are guarantee conditions stated next to the guarantee?
• Is it obvious this is an ad?

What to do this week

• Read your homepage and your three most recent ads, and highlight every factual claim.
• For each highlighted claim, find the evidence or rewrite it as a clear opinion or a specific, provable fact.
• Check your prices show VAT and any call-out or booking fee consumers always pay.
• Confirm you have permission for every testimonial you use outside the platform where it was posted.
• Bookmark the ASA Copy Advice page for your next campaign.

Marketing texts and emails have their own rules, covered in our PECR guide. And if you run paid social, see our guide to Facebook and Instagram ads. At Oski Marketing we check every ad we make for clients against these rules before it runs.