A case study is an account of how a business helped one particular customer with a particular problem, told in enough detail and with enough evidence that a prospect can judge whether the same approach would work for them. It usually follows a simple arc: the situation, what was done, and what changed as a result.
How a case study works
The structure that works best is plain. Start with the customer and the problem in their terms: a dental practice in Leeds whose new-patient enquiries had stalled, a manufacturer whose website was invisible for the products it actually sells. Then explain what you did and why you chose that approach over the alternatives. Finish with the outcome and the period it covers, measured in the numbers the customer cares about.
Good case studies include the awkward parts. A sentence on what did not work, or what you would do differently, makes the rest more believable and shows how you think. A short quote from the customer, if they are willing to give one, adds a second voice, though it is not a substitute for evidence.
Format follows use. A one-page version suits a sales email; a longer version with charts works on the website; a two-minute video interview suits social. All of them rest on the same agreed facts.
Why it matters
Buyers of services are being asked to trust you with something before they can see the result. A case study is the closest they can get to seeing it in advance. For UK businesses selling to other businesses, it is often the document a prospect forwards to colleagues to justify a shortlist.
That persuasive power is why the rules are strict. In the UK, a case study published to win customers is marketing, so the CAP Code applies: you must hold evidence for any objective claim before you publish it, and you must not mislead by exaggeration or omission. Presenting an unusually good result as typical, or leaving out that it took two years, can mislead. The Competition and Markets Authority can also act against misleading claims under consumer protection law.
Naming a client, showing their figures or using their logo also needs their permission, ideally in writing. Many clients will say yes if asked politely and shown the draft; some cannot, because of their own contracts or sector rules.
Common mistakes
- Publishing percentages with no baseline or period, such as “traffic up 300%”, which says nothing about scale or timing.
- Using figures that are rounded up, estimated or “illustrative” without saying so.
- Claiming sole credit for a result the client’s own team, a price cut or a seasonal peak also drove.
- Writing about yourself throughout, so the customer and their problem disappear.
- Naming a client or showing their logo without permission.
- Leaving the case study unlinked, so nobody reading the matching service page ever finds it.
How to act on it
Keep a simple record for every project as you go: the starting numbers, the dates, what you changed and the evidence behind each result. Writing the case study later is then straightforward, and you will be able to back any claim if challenged.
Ask the client for permission early, explain what you would like to publish and let them check the draft. If they prefer to stay anonymous, describe them by sector and region instead, and keep the figures only if they agree.
Then put the case study where buyers make decisions: link it from the relevant service page, cite it in proposals and place it next to any testimonial from the same client. Building that kind of evidence into a site’s content is part of my content SEO and strategy work, and it is one of the strongest social proof assets a service business can have.