The verdict in three sentences
A custom tool to run engagements, time and billing costs EUR 40,000 to 110,000 in 2026, versus EUR 25 to 60/user/month for a market SaaS. The tipping point sits around 20 to 30 users: below it SaaS wins, above it a custom build pays back over five years. The real question is not the purchase price but the TCO and the billable time recovered per consultant.
SaaS or custom: the five-year TCO
The classic trap is comparing a build quote to a monthly subscription. Bring both to the same horizon. For a 25-person firm, here is the 2026 order of magnitude.
| Item (25 users) | Market SaaS | Custom |
|---|---|---|
| Setup / build | EUR 3,000 | EUR 70,000 |
| Annual subscription | EUR 13,500 (45 x 25) | EUR 0 |
| Maintenance / year | included | EUR 10,500 (15 %/yr) |
| Hosting / year | included | EUR 2,400 |
| Cost over 5 years | EUR 70,500 | EUR 134,500 |
| Deep customisation | limited | full |
| Code ownership | no | yes |
Over five years SaaS stays cheaper in raw cash, but it caps customisation and the firm owns nothing. Custom is justified when specific workflows (review, supervision, automated engagement letters) recover billable time.
The features that make the difference
Not all building blocks are equal. Here are the ones that truly move a firm's productivity in 2026.
| Module | Impact | Priority |
|---|---|---|
| Engagements & deadlines | Zero tax/filing misses | Critical |
| Time entry per file | Fair billing | Critical |
| Billing & auto reminders | -30 % late payment | High |
| Client portal / DMS | -40 % emails | High |
| Profitability per engagement | Visible margin | High |
| Built-in e-signature | Faster turnaround | Medium |
| Bookkeeping connector | No double entry | Critical |
Mini case study
Sophie, partner in a 24-person firm in Dublin, bills EUR 95/hour on average. Poor time tracking loses her on average 2 unrecorded billable hours per person per week. Across 24 people and 45 weeks that is 2,160 hours, or EUR 205,200 of potentially lost revenue a year. A custom tool at EUR 70,000 that recovers just 40 % of those hours returns EUR 82,080 in year one: paid back in under 12 months.
FAQ
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How long does a custom build take?
Budget 5 to 8 months in 2026 depending on scope, with a usable first version by month 3 if you frame the MVP around engagements and time tracking.
Does custom replace my bookkeeping software?
No. It connects to your production system (via API or import) and drives engagements, time, billing and the client relationship, where market tools stay rigid.
What maintenance budget should I plan?
A maintenance fee of 15 %/year of build cost is a healthy order of magnitude, about EUR 10,500/year for a EUR 70,000 project, covering fixes, minor evolutions and security.
From how many users does custom pay off?
Between 20 and 30 users the cumulative SaaS subscriptions match the build cost over five years, especially once you value recovered billable time.
Can we start small and expand?
Yes, and it is recommended: an MVP at EUR 35,000-45,000 on the core engagements/time, then successive batches funded by the gains observed.
Let's scope your project. Tell us your headcount, your current production software and your 3 most time-consuming workflows, and we will price a realistic MVP scope with an indicative budget. 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.
