Send it at the right moment
Reply rate is decided by timing more than wording. The three moments that work: right after something lands well, attached to the final invoice, and the day the client says thank you unprompted. Two weeks later, the feeling has faded and so has your reply rate.
One more rule: never ask for "a testimonial". It sounds like homework. Ask two short questions instead.
Email — right after the work lands
Short, no pressure, no attachments.
Subject: A quick favour ([project]) Hi [name], Really glad [project] went the way it did. Would you mind answering two short questions about it? It takes about a minute and there is nothing to sign up for: [link] No pressure at all if now is a bad time. Thanks, [your name]
DM / WhatsApp
For a channel you already talk in. Shorter is better here.
Hey [name] — quick one. Would you mind writing two lines about how [project] went? Takes a minute, no login: [link] Would genuinely help me a lot.
With the invoice
The highest-reply-rate moment there is.
Subject: Invoice for [project] Hi [name], The invoice for [project] is attached. And while it is fresh — if you have a minute, two short questions about how it went: [link] Thanks again, [your name]
The follow-up: one, then stop
Around 60% of the testimonials you ever get arrive after a single nudge, sent three to five days later. A second nudge rarely converts and costs you goodwill. Send one, then let it go — and say so, which is what makes it comfortable to send.
Follow-up (send once, 3–5 days later)
Subject: Re: a quick favour ([project]) Hi [name], Just floating this back up in case it got buried — a minute of your time whenever suits: [link] If it is not a good moment, no problem at all, I will not chase it again. Thanks, [your name]
If they say yes but never write anything
This is the most common failure, and it is not laziness — a blank reply box is intimidating. Two fixes, in order of effectiveness:
- Ask questions, not for prose. Four small boxes get filled. One big one does not.
- Offer a voice note. "Just send me a 30-second voice message if that is easier" converts people who would never type a paragraph. Transcribe it yourself afterwards.
- Never send a draft to approve as the first ask. Writing their testimonial for them makes people uncomfortable and the result reads like it. Save drafting for the case study, after their words exist.
Do not ask for a favour you can return
A small, honest reciprocal line lifts replies without feeling transactional: "Happy to write one for you too, if that is useful." Only add it if you mean it.