The verdict in three sentences
A secure client portal in London costs between EUR 25,000 and EUR 45,000 for a usable MVP in 2026, and EUR 50,000 to EUR 90,000 for a full build with SSO, document management and an API. The realistic timeline is 3 to 6 months, including EU/UK hosting and data-protection compliance. A generic SaaS is cheaper upfront but hits a ceiling fast on customisation and integration with your systems.
Budget breakdown by component
A client portal is not a single flat fee: it is the sum of technical building blocks, each with its own cost. Here are the ranges seen on the London market in 2026 (order of magnitude, specialist studio, day rate GBP 500-800 / EUR 580-930).
| Component | 2026 range (EUR) | Indicative timeline |
|---|---|---|
| Authentication + SSO (SAML/OIDC) | 3,000 - 7,000 | 2-3 weeks |
| Document management (upload, versioning, permissions) | 5,000 - 12,000 | 3-5 weeks |
| Dashboard + online invoicing | 4,000 - 9,000 | 3-4 weeks |
| API + connectors (ERP, CRM) | 3,000 - 8,000 | 2-4 weeks |
| Ticketing / support module | 3,000 - 6,000 | 2-3 weeks |
| UX/UI design + responsive build | 4,000 - 9,000 | 3-4 weeks |
| Security, testing, ISO 27001 alignment | 3,000 - 7,000 | 2-3 weeks |
An MVP typically combines authentication, document management, a simple dashboard and design: EUR 25,000-45,000. The full build adds an API, ticketing, advanced invoicing, multi-role access and a security audit.
Custom build vs generic SaaS
The instinct is to compare against an off-the-shelf portal SaaS. The table below clarifies the trade-off over 3 years.
| Criterion | Custom build | Generic SaaS |
|---|---|---|
| Upfront cost | EUR 25,000 - 90,000 | EUR 0 - 5,000 |
| Recurring cost | EUR 200 - 800/month (infra) | EUR 15 - 60 / user / month |
| Customisation | Full | Limited to vendor options |
| System integration (ERP/CRM) | Native, bespoke | Standard connectors only |
| Code ownership | You | The vendor |
| 3-year cost (50 users) | ~EUR 45,000 - 100,000 | ~EUR 27,000 - 108,000 |
Below 20-30 users, SaaS is often cheaper. Above that, or as soon as your business logic leaves the beaten path, custom wins: no per-seat fee, owned code, controlled hosting and clear ISO 27001 alignment.
Mini case study
Sarah, COO of a 40-person consultancy in London, wants to replace email document exchange. She scopes an MVP at EUR 34,000 (SSO, document vault, dashboard, invoicing). The SaaS she considered charged EUR 45 per user per month for 60 client accounts, i.e. EUR 32,400/year. From year two, the custom portal pays for itself, and Sarah keeps control over hosting sensitive data and her ISO 27001 evidence trail.
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FAQ
How long does a secure client portal take to deliver?
Allow 3 to 4 months for an MVP and 5 to 6 months for a full build, including testing and a security audit. The limiting factor is usually your team's availability for system integrations.
Does data-protection compliance add much to the budget?
Compliance (UK GDPR / EU) typically represents EUR 3,000 to 7,000: regional hosting, processing records, encryption, consent management and right-to-erasure. It is unavoidable but easy to plan for.
What does SSO change in practice?
SSO (SAML or OpenID Connect) lets your clients log in with existing credentials (Microsoft, Google). It costs EUR 3,000 to 7,000 but drastically cuts forgotten-password tickets.
Can we start small and expand?
Yes, and it is recommended: ship an MVP at EUR 25,000-45,000, measure usage, then fund the next modules (API, ticketing, multi-role) in iterations of EUR 5,000 to 12,000.
What maintenance budget should I plan?
Between 12 and 18 % of the development cost per year, i.e. EUR 200 to 800/month of infrastructure plus enhancements. That is the price of continuous security and updates.
Let's scope your project. Tell us your priority blocks (SSO, documents, invoicing), your user count and an indicative budget, and we'll advise MVP or full build. 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.
