Client portal design is usually discussed as a look and is almost always decided by five structural choices made before anybody picks a colour. Who lands on the page. What the first screen shows. What the client is allowed to change. Who else at the client organisation gets in. And what happens to the account when the relationship ends. Get those right and a plain portal works. Get them wrong and a beautiful one still generates the same emails it was bought to prevent.
The first screen is a to do list, not a dashboard
Clients do not want an overview of their relationship with you. They want to know if there is anything for them to do. Open on that: what you need from them, what is ready for them, and nothing else above the fold. Everything a dashboard would have shown belongs further down or on a second screen, where the people who want it will find it and the people who do not will never be slowed by it.
Decide what the client can change, then make the rest visibly read only
Editable contact details are good, because the alternative is your records decaying. Editable dates, statuses and anything the work depends on are bad, because those are your account of what happened. Whatever you decide, make it obvious on the screen. A field that looks editable and is not generates a support message, and a field that was not meant to be editable and is generates something worse.
More than one person, and the end of the relationship
Business clients are rarely one person. Design for a second and third login from the start, each with their own credentials, rather than as an exception you handle later. And decide now what happens when the engagement ends: access removed, a window to download their own material, and a clear position on how long you keep it. Ending well is part of the design and it is the part nobody specifies.
Questions people ask about client portal design
Does client portal design mean the visual style?
Style matters far less than structure. Almost every portal that fails does so because the first screen answered the wrong question, not because it was the wrong shade of blue.
Should the portal work on a phone?
Assume most first visits are on one. If uploading a document from a phone camera is awkward, clients will wait until they are at a computer, which in practice means they will forget.
How accessible does a client portal need to be?
Treat recognised web accessibility guidance as the baseline rather than an extra. Clients with a screen reader or a keyboard only setup are still clients, and a portal they cannot use pushes work straight back to your inbox.