The verdict in three sentences
A custom client portal in London costs between £20k and £30k for a useful MVP and between £35k and £65k for a full version (documents, case tracking, invoicing, messaging). Add 8-15% of the build per year for hosting and maintenance. The real number to weigh is not the portal price but the hidden cost of email it removes: 6 to 10 hours per week per team.
What are you actually paying for in a client portal?
A B2B client portal is not a brochure site: it is a web application with authentication, role-based access, a document vault and sometimes payments. Budget follows scope, not page count.
| Scope | Features | 2026 budget (£) | Timeline |
|---|---|---|---|
| MVP | Auth + document vault + status tracking | 20k – 30k | 6 – 10 wks |
| Standard | + messaging + notifications + invoice view | 30k – 42k | 10 – 16 wks |
| Full | + online payment + e-signature + advanced RBAC | 42k – 65k | 4 – 6 mo |
| Premium | + ERP/CRM integration + mobile app | 65k – 100k | 6 – 9 mo |
The cost drivers: roles and permissions (RBAC), integration with your existing systems (billing, CRM), and security requirements (encryption, audit logging).
What recurring costs should you plan for?
The build is only the first invoice. A portal lives, evolves and must stay secure.
| Recurring item | 2026 order of magnitude | Basis |
|---|---|---|
| Hosting + infra | £70 – £320/mo | Managed cloud |
| Maintenance | 8 – 15% of build/yr | Fixes + updates |
| Monitoring & backups | £45 – £140/mo | 24/7 monitoring |
| Certificate & security | included – £500/yr | SSL, light audits |
| Annual enhancements | £2.5k – £10k/yr | New features |
For a £36k build, plan a realistic £3.5k-£5.5k/year maintenance line — the price of security and peace of mind.
Mini case study
Claire runs an HR consultancy in London, 14 staff. Her consultants spend roughly 8 hours a week sending, finding and resending documents by email to 60 active clients. At a loaded cost of £40/hour, that is £320/week, close to £15k/year of unproductive time. She invests £30k in a standard portal (documents, messaging, invoice view) plus £4.5k/year maintenance. In year one the recovered time covers half the build; full ROI lands around 15 months, before even counting the brand effect and fewer client chasers.
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FAQ
Is a custom portal more expensive than SaaS?
Short term yes: SaaS starts at £25-£70/user/month. But beyond 20-25 users and specific needs, custom (£30k one-off) is often cheaper over 3 years — and you own the code.
How long for a first usable portal?
A focused MVP (auth + documents + tracking) ships in 6 to 10 weeks. It is the best way to validate usage before committing to the full version.
Can the portal connect to our invoicing software?
Yes, via API. Integration typically adds £4k-£12k depending on the tool (Xero, QuickBooks, Sage) and the depth of sync required.
Who owns the code?
With custom, you do. Source code is delivered to you — no vendor lock-in, no risk of subscription hikes or service shutdown.
How do you secure sensitive documents?
Encryption at rest and in transit, multi-factor authentication, access logging and UK/EU hosting. These are designed in from day one, not bolted on later.
Let's scope your project. Tell us your scope (documents, invoicing, messaging), user count and 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.
