The verdict in three sentences
A practice management SaaS costs EUR 40 to 120 per staff member per month, a subscription that grows mechanically with every hire. Custom software requires EUR 30,000 to 70,000 once, plus annual maintenance of 12 to 18 %. The tipping point sits around 15 to 20 staff: beyond that, custom is amortised in 30 to 42 months and makes you the owner of your own processes.
What an accounting firm tool actually covers
A modern accounting practice tool is built on four blocks: production (files, engagements, time spent), DMS (document management), the client portal and billing. Each block carries a marginal cost and a different productivity impact.
| Module | What it does | Main gain | Weight in a custom quote |
|---|---|---|---|
| Production / engagements | File tracking, tax deadlines, time | -20 % admin hours | 30-35 % |
| DMS + invoice OCR | Auto filing, full-text search | -6 h/week of filing | 20-25 % |
| Client portal | Document upload, statements, messaging | -40 % follow-ups | 15-20 % |
| Time billing | Quotes, fees, auto reminders | +8 % collection rate | 15 % |
| Partner dashboard | Profitability per engagement and client | Data-driven decisions | 10 % |
SaaS vs custom: total cost over 5 years
The SaaS trap is its linear cost: it never drops and rises with every hire. Custom carries a high upfront cost but a gentle slope afterwards.
| Firm size | SaaS 5 years (EUR 80/staff/month) | Custom 5 years (dev + 15 %/yr) | Gap |
|---|---|---|---|
| 8 staff | EUR 38,400 | 45,000 + 27,000 = EUR 72,000 | SaaS wins |
| 15 staff | EUR 72,000 | 55,000 + 33,000 = EUR 88,000 | Roughly even |
| 20 staff | EUR 96,000 | 60,000 + 36,000 = EUR 96,000 | Tipping point |
| 30 staff | EUR 144,000 | 70,000 + 42,000 = EUR 112,000 | Custom wins |
| 45 staff | EUR 216,000 | 80,000 + 48,000 = EUR 128,000 | -41 % with custom |
These figures are a 2026 order of magnitude, excluding payroll or specific review modules. Custom also becomes an asset: you can resell it white-label or open it to other firms.
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Mini case study
Mark, a partner at a 22-staff firm in London, currently pays a SaaS at EUR 95 per head, or EUR 25,080 a year. Over 5 years that is EUR 125,400 without ever owning the tool. Custom software at EUR 62,000, plus EUR 9,300 annual maintenance, comes to EUR 108,500 over the same period. Net saving: EUR 16,900, plus a tool moulded to his review process and a client portal in his brand. He amortises custom in 37 months.
FAQ
What minimum budget to start custom software? Plan EUR 30,000 to 40,000 for an MVP centred on production and DMS, deliverable in 3 to 4 months. Portal and advanced billing modules follow in phase 2.
Is SaaS still right for a small firm? Yes. Below 12 staff, a SaaS at EUR 40-80 per head remains the most rational choice: no upfront investment, live in a few days.
How much is annual maintenance on custom software? Between 12 and 18 % of the development cost, or EUR 4,000 to 12,000 a year depending on scope. It covers fixes, regulatory updates and secure hosting.
Can I migrate data from my current SaaS? Yes, via CSV export or API. Budget EUR 3,000 to 8,000 for data migration (files, clients, time history) depending on volume and source quality.
How long for a full deployment? A 15-25 staff firm rolls out a core system in 4 to 6 months, training included. A SaaS goes live in 1 to 2 weeks but locks you into its limits.
Let's scope your project. Tell us your headcount, priority modules and indicative budget, and we will calculate the custom break-even point for your firm. 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.
