The verdict in three sentences
A custom accounting extranet costs between 25,000 and 60,000 EUR (about GBP 21,000-51,000) in 2026, delivered in 3 to 5 months. It pays back by killing email ping-pong, securing document collection and cutting admin time by around 30%. The real trade-off is not "build or not" but a shared SaaS portal versus a proprietary platform you own and can extend.
What an accounting extranet costs in 2026
The budget hinges on scope: a simple document drop-off or a genuine collaborative workspace with validation workflows.
| Scope | Key features | 2026 budget (EUR) | Timeline |
|---|---|---|---|
| Drop-off portal | Secure upload, notifications, history | 25,000 – 32,000 | 3 months |
| Standard extranet | + indexed DMS, e-signature, SSO | 33,000 – 45,000 | 4 months |
| Collaborative platform | + validation workflow, chat, dashboards | 46,000 – 60,000 | 5 months |
| Annual maintenance | Fixes, GDPR hosting, support | 15 – 20% of build | recurring |
| Practice-software connector | API to Xero, Sage, QuickBooks | 6,000 – 12,000 | +3 wks |
Custom build vs SaaS portal: the real maths
A per-seat SaaS portal looks cheaper at first, but the cumulative cost catches up with a mastered build as the firm grows.
| Criterion | SaaS portal (per seat) | Custom build |
|---|---|---|
| Year-1 cost | 8 – 15 EUR / user / month | 25,000 – 60,000 EUR once |
| 100 clients / 3 years | 28,800 – 54,000 EUR | build + ~9,000 EUR/yr maint. |
| Brand customisation | Limited | Total |
| Practice-software link | Often restricted | Dedicated API |
| Data ownership | Vendor | Firm |
| GDPR hosting (EU/UK) | Vendor-dependent | Guaranteed |
Beyond roughly 70 active users, the build becomes structurally cheaper and gives the firm an asset it owns.
Mini case study
Claire, partner at a 14-person accounting firm in the City of London, runs 240 client files. Before the extranet, each staffer spent about 5 hours a week chasing and filing documents by email: 14 × 5 × 45 weeks = 3,150 hours/year. Automating collection and reminders removes 30%, or 945 hours/year. Valued at 40 EUR/hour loaded cost, that is 37,800 EUR saved per year against a 42,000 EUR extranet: payback in about 13 months.
FAQ
Need a professional website?
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Is the portal GDPR-compliant and secure for confidential data?
Yes: EU/UK hosting, encryption at rest and in transit, full access logging. Professional confidentiality demands complete traceability, native to a custom build.
Can the extranet connect to our practice software?
Yes, via API or structured files to Xero, Sage or QuickBooks. Budget 6,000 to 12,000 EUR depending on how rich the vendor API is.
Is e-signature included?
It integrates through a qualified eIDAS provider (Yousign, DocuSign): roughly 0.50 to 2 EUR per signature, plus the technical integration inside the build budget.
How long until go-live?
Between 3 and 5 months by scope, with a first usable version (drop-off + notifications) available within 6 to 8 weeks to test with pilot clients.
What maintenance budget should we plan?
Between 15 and 20% of the build cost per year, covering fixes, security updates, hosting and user support.
Let's scope your project. Tell us your client-file volume, your practice software and your e-signature needs: we frame a scope and an indicative budget between 25,000 and 60,000 EUR. 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.
