The short answer
Ask in the contract, before the work starts. Cover two separate things: showing the work, which you may need permission for if the client owns the copyright or the job is confidential, and using their words and name as a testimonial. Keep a record of what they agreed, and don't write a testimonial for them and present it as theirs.
Showing the work
If the client owns the copyright in what you made, it's theirs to say whether you can show it (who owns the work). A confidentiality clause can also stop you describing the project. So say what you may show (screenshots, the finished piece, results), where (your website, social media, pitches), whether you may name the client, and that they can ask you in writing to stop.
Using their words
A testimonial is the client's own words. Agree that you may ask for one, and that you may quote it, with their name and company, on your website and in your marketing. Keep their message as proof. If it names an individual, that person's name and job title are personal data, so be ready to remove it if they ask.
The advertising rules say reviews must be genuine. The ASA's rule 3.44 bans fake reviews, meaning ones that purport to be based on someone's genuine experience but aren't, and rule 3.45 requires you to make clear where a review has been incentivised (ASA guidance). Those rules are written for consumer reviews, but a testimonial from a business client has to be genuine and not misleading too. Don't offer a discount in exchange for a positive review, and don't edit a testimonial to change what it says.
Sample wording
An example to adapt, not legal advice:
The Supplier may describe the services and show the finished work (but not any confidential information) in its portfolio, on its website and on social media, and may name the Client as a customer, unless the Client asks it in writing to stop. The Client agrees the Supplier may ask for feedback and quote it, with the Client's name and company, if the Client has approved the wording.
In AgreeVia
Some templates, such as the Agency Retainer Agreement and the Event Photography & Video Agreement, have terms for portfolio use. For others, such as the Freelance Services Agreement, add the permission to the description of the work, or send a short note with the wording above as an uploaded PDF and place a signature box for the client.
Questions people ask
Can I put a client's logo on my website?
Ask first. A logo is usually protected by trade mark and copyright, so agree in writing that you may show it, and where.
Can the client ask me to take the work down?
If you write that into the permission, yes, and it is a good thing to offer. It makes clients readier to agree.
Can I ask for a testimonial in the contract?
You can agree in the contract that you may ask for one and quote it once they've approved the words. The words themselves come after the work.
This guide explains the general position in the UK as we understand it on 25 October 2026. The law differs between England and Wales, Scotland and Northern Ireland, and it changes. If something important turns on it, talk to a solicitor or an accountant.
Templates and tools for this
Send your first agreement free
Send a contract with your portfolio permission in it, and have your client sign it from a link.
Free for 3 documents a month, no card needed. AgreeVia works in your browser and is live on Google Play. Coming soon to the App Store.