Word of mouth marketing is getting customers and fans to recommend you to other people, in person or online. Unprompted recommendations are simply word of mouth, but once a business pays or rewards someone for a mention, UK rules expect it to be clearly identifiable as an ad.
Word of mouth is the oldest marketing channel there is, and still the one people trust most when it's real. A friend saying 'use this plumber' carries weight no ad can buy. The catch is in that phrase 'when it's real'. The moment a business starts nudging recommendations along with payments, freebies or commission, the recommendation starts to look like an ad, and in the UK the rules treat it as one.
This page splits word of mouth into two kinds, organic and incentivised, and explains where the line sits under UK advertising rules. One note up front: this is the UK regulator's view, from the Advertising Standards Authority (ASA) and the CAP Code it applies. Other countries have their own rules, so check the regulator where your customers are.
Organic recommendations versus incentivised ones
Organic word of mouth happens when someone talks about you because they want to: a happy customer, a review left unprompted, a colleague passing your name on. Nobody's paying them and you don't control what they say.
Incentivised word of mouth is anything you encourage with a reward: referral discounts, affiliate commission, free products for creators, paid mentions. It can work brilliantly. It also changes what the audience is entitled to know.
| Type | Example | Needs to be clearly identifiable as an ad? |
|---|---|---|
| Organic | A customer recommends you to a friend unprompted | No |
| Gifted or paid creator mention | A creator posts about a product you sent or paid them to cover | Yes, under the ASA's guidance |
| Affiliate link or code | A creator earns commission on sales through their link | Yes; the ASA treats the content as advertising |
| Connected person | An owner, employee or shareholder posts about the brand | Yes, where they're commercially or personally connected |
When a mention becomes an ad in the UK
The ASA's guidance on recognising ads in social media and influencer marketing is clear on the trigger. Whenever a brand gives an influencer a payment or any other incentive, requested or unsolicited, or the influencer is otherwise personally or commercially connected to the brand, any content featuring or referring to the brand needs to be obviously identifiable as advertising. The ASA notes this is a requirement under consumer protection law, enforced by the Competition and Markets Authority and Trading Standards.
When the brand also has editorial control over the content, the ASA can act under the CAP Code as well, and if an advertorial is found to breach the Code, both the influencer and the brand are named in the ruling.
Affiliate links are their own case. The guidance says that when an influencer includes an affiliate link or code, they're acting as an advertiser, so any content referring to that product counts as advertising. The ASA typically treats the brand as at least jointly responsible, whether or not it knew about or controlled the specific content.
And it doesn't take a big audience. The ASA says there isn't a particular number of followers that makes someone an influencer; it defines one as any human, animal or virtually produced persona active on a social media platform. If you're working with creators on purpose, our guide to the basics of influencer marketing covers the wider picture.
Labels the ASA expects to see
The ASA's research on labelling influencer advertising found that ads should be disclosed and clearly labelled, with 'ad' or '#ad' used at a minimum. Its advice on making clear that an ad is an ad adds that people typically struggle to identify when influencer posts are ads, so the ASA is likely to expect a prominent label upfront, which usually means at the beginning.
- Likely acceptable: 'Ad', 'Advert', 'Advertising', 'Ad Feature', and 'Advertisement Feature' for advertorials, with or without a '#'.
- Unlikely to be clear enough: 'Supported by', 'Funded by', 'Gifted', 'In association with' or 'Thanks to X for making this possible'.
- Too obscure: abbreviations like 'aff' or 'sp', and the word 'affiliate' on its own.
- Not enough by itself: tagging the brand with an @ mention, a personalised discount code, or a note in your bio.
- Badly placed: a label buried in a block of hashtags at the end, or hidden behind 'See more'.
Platform tools can help. The ASA says a built-in label such as Instagram's 'Paid partnership' may be sufficient if it's upfront, clear and prominent, though its research found it may not be enough on its own. If you're not sure, add 'Ad' as well.
Want AI doing the heavy lifting in your marketing?
I build the systems that handle the boring 80 percent, so you get your week back. Done properly, with the human kept in.
Take extra care with children. The ASA's advice notes that under-12s often struggle to recognise highly integrated marketing online, so disclosures aimed at them need to be prominent, appear as the ad starts or before, and make the marketer's identity clear.
Encouraging referrals without crossing the line
None of this means you should stop encouraging word of mouth. It means being deliberate about which kind you're running. Here's how I'd approach it:
- Earn the organic kind first. Make the product and service worth talking about, then make sharing easy: a short link to leave a review, a line in your follow-up email asking people to pass your name on. Asking isn't the same as rewarding.
- If you reward people for posting, I'd treat their public posts the way the ASA treats an influencer's and ask them to label them as ads.
- Brief creators on labelling in writing before they post, and check the live posts. The ASA names both brand and influencer when an advertorial breaks the Code.
- Give affiliates clear disclosure instructions, since the ASA usually holds the brand at least jointly responsible.
- Remember the rest of the Code. The ASA reminds marketers that labelling isn't the only requirement; ads still mustn't mislead consumers or cause serious or widespread offence.
If you want to run a structured referral scheme, our roundup of referral program software covers tools that track rewards for you. And if you're thinking about stunts designed to get people talking, our guide to low-budget guerrilla tactics covers that end of word of mouth, including why a stunt can still count as advertising.
Outside the UK
Everything above comes from the UK regulator. The ASA describes its rules as largely media-neutral, so they apply to new platforms and formats as they appear. The principle travels well too, since audiences everywhere deserve to know when a recommendation was paid for, but the exact rules, labels and enforcement differ by country. If your customers are elsewhere, check the advertising regulator and consumer protection rules there.
Quick answers
Is word of mouth marketing regulated?
Organic recommendations aren't advertising. Under UK rules, once a brand gives someone a payment or other incentive, or they're commercially connected to the brand, content about it needs to be obviously identifiable as an ad.
Does a gifted product count?
The ASA's guidance says any payment or other incentive, requested or unsolicited, means content about the brand must be identifiable as advertising. It also says 'Gifted' on its own is unlikely to be a clear enough label.
Is #ad at the end of a post enough?
Not if it's buried among hashtags or hidden behind 'See more'. The ASA expects a prominent label upfront, though it says a label at the end may be acceptable on very short posts.
Do these rules apply outside the UK?
These are the ASA's rules for UK advertising. Other countries have their own regulators and laws, so check the rules where your audience lives.
