The verdict in three sentences
A custom client portal in London costs, in 2026, between 25,000 and 60,000 EUR for an MVP and 60,000 to 150,000 EUR for a full build (documents, billing, tickets, notifications). SSO authentication adds about 8,000 EUR, delivery runs 10 to 20 weeks, and evolutive maintenance (TMA) represents 12 to 18% of the build per year. The real ROI case is built on reduced support load and saved admin time, not on a license price.
What a client portal actually covers
A client portal is not just a login screen: it is a business application that centralises the customer relationship. The most requested building blocks in 2026 are the document space (contracts, invoices, certificates), ticket/request tracking, online billing and notifications. Each block has its own development cost, and it is by assembling your scope that you get a realistic budget rather than a catch-all package.
| Module | Indicative 2026 cost (EUR) | Expected support gain |
|---|---|---|
| Authentication + account management | 6,000 - 12,000 | Essential base |
| SSO / enterprise login | 8,000 | -20% access tickets |
| Document space (DMS) | 9,000 - 18,000 | -35% document requests |
| Billing + online payment | 12,000 - 25,000 | -30% chasing |
| Ticketing / support | 8,000 - 16,000 | -25% inbound calls |
| Email/SMS notifications | 4,000 - 8,000 | -15% manual follow-ups |
| Admin dashboard | 7,000 - 14,000 | Centralised control |
| API connection (ERP/CRM) | 10,000 - 30,000 | Zero double entry |
MVP, full build and 3-year total cost
The classic trap is comparing an MVP quote to a full-build quote. The MVP must solve one acute problem (for example: stop invoice requests by email), not cover the whole scope. The full build comes later, once usage is validated. Over three years, maintenance weighs as much as the initial build: budget for it from day one.
| Item | MVP | Full build |
|---|---|---|
| Initial development | 25,000 - 60,000 EUR | 60,000 - 150,000 EUR |
| Timeline | 10 - 14 weeks | 16 - 20 weeks |
| SSO | Optional (+8,000) | Included |
| Annual TMA (12-18%) | 4,500 - 9,000 EUR | 9,000 - 22,500 EUR |
| 3-year total cost (estimate) | 40,000 - 90,000 EUR | 90,000 - 220,000 EUR |
Mini case study
Mark is IT director of a B2B services SME in London with 4,200 active customers. His support team handles roughly 900 requests per month, of which 40% concern documents or invoices (360 requests). Each request takes on average 9 minutes, or 54 hours per month, at a loaded cost of 35 EUR/hour — about 1,890 EUR/month on that single driver. He invests 72,000 EUR in a full portal with DMS and billing, plus 11,000 EUR annual TMA. By eliminating 80% of those requests, he saves 1,512 EUR/month (18,144 EUR/year), on top of fewer overdue-invoice chases. Payback lands between 30 and 42 months on support alone, faster once online-payment cash-flow gains are counted.
FAQ
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What is the minimum budget to start seriously?
Budget 25,000 EUR for a credible MVP with authentication, a document space and an admin dashboard. Below that, you get an unmaintainable prototype that will cost more to rebuild.
Is SSO really necessary?
For a B2B portal aimed at corporate customers, SSO (about 8,000 EUR) cuts roughly 20% of access tickets and reassures client IT teams on security. For a consumer-facing portal, standard authentication is often enough.
How much is annual maintenance?
TMA represents 12 to 18% of the build cost per year, i.e. 9,000 to 22,500 EUR for a 100,000 EUR portal. It covers fixes, security upgrades and small enhancements.
What is a realistic timeline to go live?
Between 10 and 14 weeks for an MVP and 16 to 20 weeks for a full build, including ERP/CRM integrations. Connections to existing systems are the main factor that extends timelines.
Can the portal connect to our ERP?
Yes, via API. Budget 10,000 to 30,000 EUR depending on ERP maturity and the number of flows (customers, invoices, stock). This is the investment that removes double entry and makes data reliable.
Let's scope your project. Tell us your scope (modules, number of users, integrations), your indicative budget and target timeline: we frame an MVP and a full-build path. Detailed quote within 48 h. WhatsApp +221 77 596 93 33.
Mohamed Bah
Fondateur, Kolonell
Passionate about digital and entrepreneurship in Africa, Mohamed has been helping Sénégalese businesses with their digital transformation since 2020. Founder of Kolonell, he believes every SME deserves a professional and accessible online présence.
