The verdict in three sentences
A custom client portal for an accounting firm costs between 15,000 and 45,000 EUR to build, with annual maintenance of 12 to 18%. Below 30 active users, a SaaS document-management platform at 15-40 EUR/user/month stays cheaper; beyond that, custom amortises and you own your data. The real decision hinges on e-signature, GDPR compliance and integration with your accounting production software.
What an accounting client portal covers in 2026
The standard scope goes well beyond file drop-off. A firm expects a structured document store (by client, by fiscal year, by document type), a digital vault, e-signature for engagement letters and financial statements, and automated reminder notifications.
| Module | Complexity | Range (EUR) | Indicative lead time |
|---|---|---|---|
| Auth + partitioned client spaces | Medium | 3,500 - 6,000 | 3-4 wks |
| Classified document store (client/year/type) | High | 4,000 - 9,000 | 4-6 wks |
| E-signature (eIDAS) | Medium | 3,000 - 6,500 | 2-4 wks |
| Digital vault + timestamping | High | 2,500 - 7,000 | 3-5 wks |
| Notifications + automated reminders | Low | 1,500 - 3,500 | 1-2 wks |
| Accounting-software connector (API) | High | 3,500 - 10,000 | 4-8 wks |
The overall lead time for a full project is 3 to 5 months, integration included. Budget a 2-3 week scoping phase before any development.
Build vs buy: the three-year comparison
For a firm of 40 users (staff + active clients), here is the 2026 order of magnitude over 36 months.
| Item | SaaS DMS (30 EUR/user/month) | Custom (30,000 EUR build) |
|---|---|---|
| Upfront cost | 0 | 30,000 EUR |
| 36-month subscription (40 users) | 43,200 EUR | 0 |
| 36-month maintenance/hosting | Included | 12,960 EUR (14%/yr) |
| Business-specific customisation | Limited | Total |
| Data ownership | No | Yes |
| 3-year total | 43,200 EUR | 42,960 EUR |
At 40 users the two models converge. Below 30 users SaaS wins; beyond 50 custom pulls ahead year after year, because the subscription grows linearly while the build is a fixed cost.
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Mini case study
Mr Rousseau runs a firm of 9 staff and 210 clients in Bordeaux. On SaaS at 30 EUR/user for 25 internal seats, he pays 9,000 EUR/year, but cannot link the tool to his production software. He chooses a custom portal at 28,000 EUR with an API connector. Maintenance 14%/yr = 3,920 EUR. Over 4 years: SaaS = 36,000 EUR with no integration; custom = 28,000 + 15,680 = 43,680 EUR but with 8 hours/week saved (no re-keying), i.e. ~1,600 hours over 4 years valued at 45 EUR = 72,000 EUR in gains. Payback reached in 18 months.
FAQ
Isn't SaaS enough for a small firm? Yes, below 30 active users and without deep integration needs, a SaaS at 15-40 EUR/user/month is the rational choice: deployed in days, zero maintenance on your side.
Is e-signature mandatory? No, but it saves considerable time: an electronically signed engagement letter costs roughly 0.50 to 2 EUR versus 3-5 days of postal back-and-forth. The module costs 3,000 to 6,500 EUR in custom.
How do you ensure GDPR compliance? EU hosting, encryption at rest and in transit, access logging and configurable retention periods. Budget 2,000 to 4,000 EUR for an audit and documentary compliance.
What maintenance budget should I plan? Count 12 to 18% of the build cost per year: fixes, security updates, minor evolutions and hosting. On a 30,000 EUR project, that is 3,600 to 5,400 EUR/year.
Can we start with an MVP? Yes. An auth + document store + notifications core ships in 6-8 weeks for 10,000 to 15,000 EUR, then you add e-signature and connectors by iteration.
Let's scope your project. Tell us your active-client count, your accounting production software and your e-signature needs: we'll price a custom portal or point you to the right SaaS. 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.
