The verdict in three sentences
Custom management software for an accounting firm costs between 50 000 and 150 000 EUR in 2026, depending on the number of modules and how deeply it integrates with your production tool. The price gap comes not from screen count but from connectors (Cegid, ACD, e-invoicing) and the secure client portal. Expect 4 to 8 months before a first production release usable by every staff member.
Why go custom when vertical suites exist
Vertical suites cover accounting production but leave gaps: engagement-letter tracking, re-billing of diligences, per-file profitability, client onboarding. A firm of 15 to 60 staff ends up stacking spreadsheets, emails and disconnected SaaS. Custom software consolidates that scope into a single tool connected to your production suite, without replacing it.
The budget-smart move: don't rebuild everything. Keep production in Cegid or ACD, and build the firm layer (client relationship, workflow, steering) on top via API or export.
Firm modules and unit cost (2026 order of magnitude)
| Module | Scope | Cost | Timeline |
|---|---|---|---|
| Core + authentication | Staff roles, multi-office, audit log | 8 000 - 14 000 EUR | 3-4 wks |
| Document management | Per-file filing, search, versions | 9 000 - 18 000 EUR | 4-6 wks |
| Engagement-letter workflow | Templates, approval circuit, signature | 7 000 - 15 000 EUR | 3-5 wks |
| Client portal | Document upload, deadlines, messaging | 12 000 - 25 000 EUR | 5-7 wks |
| Per-file profitability | Time spent, budget vs actual, alerts | 8 000 - 16 000 EUR | 4-5 wks |
| Production connector (Cegid/ACD) | Sync clients, trial balances, invoices | 6 000 - 18 000 EUR | 3-6 wks |
| Billing & re-billing | Quotes, fees, reminders | 6 000 - 14 000 EUR | 3-5 wks |
Firms rarely start with every module. A first batch of Core + DMS + Client portal + Connector lands around 45 000 to 70 000 EUR, then you iterate.
What pushes the bill up
| Factor | Budget impact |
|---|---|
| Real-time Cegid connector (API) vs CSV export | +8 000 to +14 000 EUR |
| Qualified eIDAS e-signature | +4 000 to +9 000 EUR |
| Migration of historical documents (GBs) | +5 000 to +12 000 EUR |
| Client mobile app (iOS + Android) | +12 000 to +22 000 EUR |
| Sovereign hosting + DR plan | +200 to +600 EUR/month |
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Mini case study
Claire, partner at a 28-staff firm in Nantes, wastes significant time chasing documents and tracking engagements. She commissions a Client portal + Workflow + ACD connector core for 58 000 EUR. Measured at 6 months: document-collection time per file drops from 40 to 18 minutes. Across 900 files a year, that is roughly 330 hours recovered, close to 13 000 EUR of payroll redeployed to billable advisory. The tool pays for itself in under three fiscal years, before any client-image gain.
FAQ
Can we keep Cegid and add custom software? Yes, that is the recommended scenario. The connector syncs clients, trial balances and invoices via API or export, for 6 000 to 18 000 EUR depending on the real-time level.
How long until first production release? Expect 4 to 8 months for a functional batch usable firm-wide. We deliver in increments every 2 to 3 weeks, not in one big bang.
What annual maintenance should we budget? As an order of magnitude, 12 to 18 % of development cost per year, i.e. 6 000 to 15 000 EUR covering evolutions, security and support.
Is e-signature included? It is an option since it depends on an eIDAS provider. Budget 4 000 to 9 000 EUR of integration plus a per-signature fee.
Do we own the code? Yes, in a custom project the source code is yours, which protects you from lock-in to a single vendor.
Let's scope your project. Tell us your priority modules, current production tool and target budget, and we'll frame an amortizable first batch. 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.
