The verdict in three sentences
A bespoke secure client portal for an accounting firm in London sits in 2026 between 18,000 and 40,000 EUR, depending on the number of modules (vault, e-signature, SSO, notifications). The real gain isn't cosmetic: it's up to 40% fewer emails and client follow-ups, meaning staff time returned to actual accounting work. Budget 3 to 5 months and a maintenance retainer of 500-900 EUR/month to keep compliance and security current.
What the budget covers by tier
A firm of 8 to 20 staff has different needs than a multi-office practice. Here are the 2026 ballpark figures on the bespoke market.
| Tier | Functional scope | Indicative price (EUR) | Timeline |
|---|---|---|---|
| Essential | Upload/download of documents, per-client space, email notifications | 18,000 - 24,000 | 3 months |
| Standard | + digital vault, e-signature, automated reminders | 24,000 - 32,000 | 4 months |
| Advanced | + SSO/OAuth, connector to practice software, dashboard | 32,000 - 40,000 | 5 months |
| Extended bespoke | + mobile app, advanced DMS, multi-office | 40,000 - 55,000 | 6 months |
The line item that swings a quote is almost always the integration with your practice software and qualified e-signature (eIDAS), not the design.
Total cost over 3 years (TCO)
Development is only part of the equation. Security for a portal holding tax files requires continuous operations.
| Item | Year 1 | Years 2-3 (per year) |
|---|---|---|
| Initial development | 30,000 EUR | — |
| Secure EU hosting + backups | 2,400 EUR | 2,400 EUR |
| Maintenance (security, evolutions) | 8,400 EUR | 8,400 EUR |
| E-signature (subscription + per act) | 1,800 EUR | 1,800 EUR |
| Total | 42,600 EUR | 12,600 EUR |
Over 3 years the TCO lands around 67,800 EUR, i.e. an average of 22,600 EUR/year for an asset that structurally cuts administrative load.
Mini case study
Sophie, partner at a 14-person accounting firm in central London, handles 320 client files. Before the portal, each staff member spends about 5 hrs/week sending, chasing and retrieving documents by email. At a loaded cost of 35 EUR/hr, that's 14 x 5 x 35 = 2,450 EUR/week, or ~110,000 EUR/year.
A 40% reduction in that admin time saves 44,000 EUR/year. Against a portal investment of 30,000 EUR plus 12,600 EUR of annual costs, the payback is under 12 months — before counting the improved client experience.
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FAQ
Is bespoke really better than an off-the-shelf SaaS?
Below 8 staff, a SaaS at 30-60 EUR/month/user is often enough. Beyond that, once you want a connector to your practice software and your own branding, bespoke pays off from around 250 active files.
Is e-signature included in the price?
The integration module is, but qualified eIDAS signature relies on a third-party provider billed on subscription (about 80-150 EUR/month) plus a per-act cost of 0.50 to 2 EUR depending on volume.
Where is my clients' tax data hosted?
On EU-based hosting, with encryption at rest and in transit, access logging and daily backups. Budget about 200 EUR/month for compliant hosting sized for a firm.
How long until go-live?
Between 3 and 5 months depending on module count and integration complexity. An Essential tier can ship in 3 months if the scope is frozen at kickoff.
What maintenance budget should I plan?
Between 500 and 900 EUR/month, covering security fixes, regulatory updates and small improvements. It's a non-negotiable line for a portal handling sensitive data.
Let's scope your project. Tell us your file count, your practice software and priority modules (vault, signature, SSO) and we'll frame the scope. 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.
