How to Write a Customer Case Study (Without Making Up Results)

How do you write a customer case study?

You write a customer case study by interviewing a real customer about a real result, then telling their story in four parts: the situation they were in, the decision they made, what changed, and what comes next. Get their written permission first. Collect their numbers, screenshots, and exact words before you start writing, and build the story only from those. Send the draft back for approval before you publish. The whole job is accuracy: a case study is only persuasive because the reader can believe it.

A testimonial is a sentence or two. A case study is the longer version, with enough detail that a prospect in the same position can picture themselves in it. That detail is also the risk, because detail is where people are tempted to embellish. The method below is built to prevent that.

Case study or testimonial: which do you need?

Use a testimonial when you need a quick piece of proof next to a button. Use a case study when a buyer is weighing a bigger decision and wants to see how the thing worked in a situation like theirs. If you do not have testimonials yet, start there: [how to get testimonials](/blog/how-to-get-testimonials) covers collecting them. Case studies usually grow out of the best testimonial you already have, by asking that customer for a longer conversation.

The Receipts-First method

Receipts-First is the routine I set up with clients so a case study never contains a claim they cannot support. The order matters: receipts, then story, never the other way around.

Pick the right customer

The best case study subject is not your biggest customer. It is a customer who looks like the buyer you want next, got a real and specific result, and is willing to talk about it. A relatable customer with a modest, clear outcome is more useful to a prospect than an impressive outlier they cannot see themselves in.

• They resemble your next buyer in situation and size, not just in industry.
• They can point to something concrete that changed, even if it is small.
• They are comfortable being named, or comfortable being described without a name.
• They are still happy. Do not chase a case study from someone who has gone quiet.

The five interview questions

A 20 to 30 minute conversation is enough. Record it with their permission, and ask these five questions in order.

1. "What was going on before you started?" This is the situation. Ask what it was costing them in time, money, or stress, in their words.
2. "What had you already tried, and why did you choose this?" This is the decision. It is also the doubt your next buyer has.
3. "What did you actually do?" This is the how. Ask for the specific steps, so the reader sees the path.
4. "What changed, and how do you know?" This is the result. Ask what they can show: a number, a screenshot, a before and after. If they cannot show it, treat it as opinion, not data.
5. "What would you tell someone in the position you were in?" This is the closing line, in their voice.

Question four is where honesty matters most. If the customer says it feels better but has no numbers, write that. "Feels better" is a true result. An invented percentage is not. [How to handle sales objections](/blog/how-to-handle-sales-objections) is a useful companion, because the doubts you hear in question two are the objections your page needs to answer.

How to structure the case study

Keep it short enough that a busy prospect finishes it. Open with a one or two sentence summary that states the customer, the problem, and the result, so a skimmer gets the point. Then use four short sections.

• Situation: who the customer is and what was going wrong, in specifics.
• Decision: what they considered and why they chose your offer.
• Result: what changed, with only the receipts they gave you. Pull quotes straight from the interview.
• What is next: what they are doing now, and the line from question five.

Write it in plain language and in the customer's voice where you can. Do not add adjectives the customer did not use. If a result needs context to be fair, such as a customer who already had an audience before they started, include the context. A prospect who later discovers the missing context will trust you less, not more.

How to draft a case study with Claude

Claude is useful for the grind: cleaning up an interview transcript, pulling out the exact quotes, and turning your notes into a first draft. Use the Claude desktop app, and keep it on a short leash.

1. Paste the transcript and tell Claude to quote only text that appears in it, word for word.
2. Ask it to list every claim in your draft next to the line in the transcript or the receipt that supports it. Anything it cannot match gets cut.
3. Ask for the four-section draft, using only the facts and quotes you supplied.
4. Ask it to flag any adjective, number, or outcome that is not in the source material.
5. Send the draft to the customer. Their approval is the final check, not the model's.

The rules to follow: permission and honest results

In the United States, the Federal Trade Commission's rule on consumer reviews and testimonials, in effect since October 21, 2024, prohibits fake or false testimonials, and the FTC's own guidance says courts can impose civil penalties for knowing violations. A case study is a long testimonial, so the same logic applies: it has to describe a real customer's real experience.

• Real customer, real result. Never composite, invent, or rename a customer and present it as a real one.
• Do not tie a reward to what the customer says. If you give them something for their time, give it regardless of what they say, and disclose it.
• Be careful with results. A specific result in a case study will usually be read as what others can expect, and a small disclaimer does not change that. Be clear about the customer's starting point and what buyers can generally expect.
• Keep the permission email on file, and take the case study down promptly if the customer asks.

This is a plain-language summary, not legal advice. Read the FTC's guidance yourself, and check the rules in any other country where you sell.

Where to use a case study

Put the full case study on its own page, then use pieces of it where they answer a doubt. A one-line result and a link belong on your [sales page](/blog/how-to-write-a-sales-page) near the price. A short version fits in a launch or welcome email; [how to write a launch email sequence](/blog/how-to-write-a-launch-email-sequence) covers where proof fits. You can also turn one case study into several posts and clips; [how to repurpose content with AI](/blog/how-to-repurpose-content-with-ai) shows how, as long as every repurposed claim still matches the approved version.