Custom client portal cost in London in 2026: scope and budget

The verdict in three sentences

A custom client portal in London costs, in 2026, between 18,000 and 35,000 EUR for a solid MVP (authentication, documents, invoices, tickets), delivered in 10 to 16 weeks. Ongoing maintenance runs between 400 and 1,200 EUR/month depending on traffic and the number of integrations. The payback is fast: -30% support calls and +15% retention are enough to recoup the project in under 12 months.

What an MVP client portal covers

A client portal is not a brochure site: it is an authenticated application where each client finds their documents, invoices and requests. A 2026 MVP scope breaks down into clear line items, with the following ballpark for a London-based services SME.

A serious MVP therefore lands in the 18,000 - 35,000 EUR range. Below 15,000 EUR you get a configured template, not a custom portal: integrations and fine-grained role management disappear.

Custom vs SaaS client portal

Many vendors offer a client portal on subscription. The maths shifts with duration and how specific your business rules are.

Custom becomes worthwhile when your processes are specific (approval workflow, connection to your billing tool, business rules) or when user count makes the SaaS subscription balloon. Below 200 clients with standard needs, SaaS is often cheaper in year one.

Mini case study

Claire runs the customer service team of an industrial SME in London, 9 people on support. Her teams handle around 1,400 calls/month, many about invoice requests and order tracking. Fully loaded cost per handled call: estimated 6 EUR (agent time plus tooling).

She invests 26,000 EUR in a custom MVP portal plus 700 EUR/month maintenance. The portal removes 30% of calls, i.e. 420 calls/month saved: 420 x 6 = 2,520 EUR/month, minus maintenance, leaving a net gain of 1,820 EUR/month. The portal pays back in 26,000 / 1,820 ≈ 14.3 months, before counting the +15% retention that adds several thousand euros of margin on an average annual basket.

FAQ

What is the minimum budget for a credible client portal in 2026?

Budget 18,000 EUR for an MVP with authentication, documents and billing. Below 15,000 EUR you get a configured template with limited integrations, rarely enough to cut calls by 30%.

How long to deliver?

Between 10 and 16 weeks for an MVP. Discovery takes 1-2 weeks, development 6-10, and QA plus go-live 2-3 weeks.

What does maintenance cost?

Maintenance ranges from 400 to 1,200 EUR/month: secure hosting, fixes, security updates and small enhancements. For a high-traffic portal with several integrations, expect the top of the range.

Can you connect our billing software?

Yes, via API or export/import. Billing integration represents 3,000 to 6,500 EUR depending on the richness of the existing API and the need for real-time sync.

What ROI can we realistically expect?

A realistic target is -30% support calls and +15% retention. For a support desk handling 1,400 calls/month at 6 EUR each, that is about 2,520 EUR/month of agent time saved.

Let's scope your project. Share your client count, your integrations (billing, CRM) and your target date: we price an MVP between 18,000 and 35,000 EUR. Detailed quote within 48 h. WhatsApp +221 77 596 93 33.