The verdict in three sentences
A custom client portal for a London or Paris services firm budgets at EUR 25,000 to 70,000 excl. VAT (about GBP 21,000 to 60,000) depending on modules, authentication and integrations. The cost driver is not the interface but integration with billing and CRM. Plan 12 to 16 weeks of delivery and maintenance of about 15% per year of the initial build.
What a B2B client portal includes in 2026
The CFO of a services company managing 800 client accounts wants to remove three pain points: requests for invoice copies, searches for signed contracts and ticket follow-up by email. The portal therefore exposes data that already lives elsewhere (ERP, billing tool, helpdesk), with fine-grained rights per client and per user.
| Module | Functional scope | Indicative 2026 budget (EUR excl. VAT) |
|---|---|---|
| Authentication and roles | Login, MFA, admin / user / read-only roles | 3,000 to 6,000 |
| Enterprise SSO | SAML or OpenID Connect (Azure AD, Google Workspace) | 4,000 to 9,000 |
| Invoices and payments | List, PDF, status, online card or direct debit payment | 5,000 to 12,000 |
| Contracts and documents | Light document management, versions, e-signature | 4,000 to 10,000 |
| Support tickets | Creation, tracking, attachments, helpdesk sync | 5,000 to 11,000 |
| Client dashboard | Usage indicators, renewals, alerts | 3,000 to 8,000 |
| Back office and audit log | Account management, GDPR traceability | 3,000 to 7,000 |
An "invoices + tickets + roles" scope lands around EUR 25,000 to 35,000. With SSO, e-signature and dashboard, expect EUR 50,000 to 70,000.
The three budget scenarios
| Criterion | Essential | Standard | Advanced |
|---|---|---|---|
| Initial budget (EUR excl. VAT) | 25,000 to 35,000 | 35,000 to 50,000 | 50,000 to 70,000 |
| Timeline | 10 to 12 weeks | 12 to 14 weeks | 14 to 16 weeks |
| Modules | Invoices, tickets, roles | + contracts, documents, payment | + SSO, e-signature, dashboard |
| Integrations | 1 (billing) | 2 (billing, helpdesk) | 3 to 4 (ERP, CRM, helpdesk, e-signature) |
| Monthly hosting | EUR 80 to 150 | EUR 150 to 300 | EUR 300 to 600 |
| Annual maintenance (15%) | EUR 3,750 to 5,250 | EUR 5,250 to 7,500 | EUR 7,500 to 10,500 |
Senior agency developer day rates in London and Paris sit around EUR 600 to 850 per day in 2026. Large gaps between quotes usually come from the quality of existing APIs: a billing tool without a documented API can add 8 to 15 days of work.
What actually lowers support costs
Services firms that open a portal typically see, as a 2026 order of magnitude, 30 to 50% fewer support calls and emails about documents and status. The gain depends on adoption: aim for 60% active clients in the first six months, with a personal invitation, a link in every invoice and a two-minute video tutorial.
Other checkpoints: UK or EU hosting, an access log for GDPR, daily backups and a penetration test before go-live (budget EUR 5,000 to 10,000).
Mini case study
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Claire, CFO of an IT services firm, has 800 clients and a 4-person support team handling 1,200 requests per month, 45% of them about invoices, contracts or ticket status. The Standard portal costs EUR 42,000 plus EUR 6,300 of annual maintenance. If 40% of those 540 requests disappear, that is 216 requests at 12 minutes each, the team recovers 43 hours a month, about EUR 20,000 per year at EUR 38 per loaded hour. Add 5 fewer days of payment delay thanks to online payment, and payback arrives around 24 months.
FAQ
How much does a simple client portal cost?
A portal limited to invoices, tickets and role management starts around EUR 25,000 excl. VAT. Below that, you are usually looking at a configured SaaS tool rather than custom development.
Do we need SSO in the first release?
Only if your clients are large accounts that require it. SSO adds EUR 4,000 to 9,000 and can ship in phase 2, three months after launch.
How long from contract to go-live?
Plan 12 to 16 weeks, including 2 weeks of scoping and 2 weeks of acceptance testing. Integration with a legacy ERP is the leading cause of delay.
What does maintenance cost after delivery?
Maintenance runs at about 15% of the initial budget per year, so EUR 6,000 for a EUR 40,000 project. It covers fixes, security updates and small enhancements.
Wouldn't an off-the-shelf portal SaaS be cheaper?
For fewer than 100 clients, often yes, from EUR 300 to 800 per month. Beyond 500 clients with specific integrations, custom becomes more cost-effective over 4 to 5 years.
Let's scope your project. Send us your priority modules and existing tools, and we will price a scope between EUR 25,000 and 70,000 with a 12 to 16 week plan. 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.
