The verdict in three sentences
If your invoicing fits a standard flow (quote, invoice, reminder), a SaaS at 39-149 EUR/month covers 80 % of the need and pays off within weeks. If you have an ERP, specific bank reconciliation, or business-rule reminders, custom automation at 8,000-18,000 EUR repays its cost in 5 to 9 months. Either way, the target figure is the same: cut DSO from 62 to 41 days and reclaim 6 to 10 hours per week.
SaaS vs custom: the real 2026 comparison
SaaS suites (Pennylane, Sellsy, Qonto Invoicing) cover compliant e-invoicing, automatic reminders, and basic bank reconciliation. Custom becomes relevant as soon as you connect an ERP, apply segment-based reminder scales, or orchestrate several tools.
| Criterion | SaaS (Pennylane/Sellsy) | Custom (script + API) |
|---|---|---|
| Entry cost | 39-149 EUR/month | 8,000-18,000 EUR |
| Setup | 1-3 days | 3-6 weeks |
| Reminders D+7/D+15/D+30 | Standard | Custom per segment |
| ERP connection | Limited | Full (API/webhooks) |
| Bank reconciliation | Basic | Advanced business rules |
| Maintenance / changes | Included (capped) | 250-500 EUR/month |
| Code ownership | No | Yes |
Hours and cash flow gains, quantified
Automation works on two levers: admin time and payment delay (DSO). Every DSO day saved is cash coming in faster.
| Metric | Before (manual) | After (automated) |
|---|---|---|
| Invoicing time/week | 6-10 h | 1-2 h |
| Reminders sent on time | 55 % | 98 % |
| Average DSO | 62 days | 41 days |
| Invoices >30 days late | 22 % | 9 % |
| Data-entry errors | 4-6 % | < 1 % |
| FTEs involved | 2 (partial) | 0.5 |
Mini case study
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Claire, finance director of a 45-person industrial SME in Lyon, invoices 380 clients/month. Two accountants each spend 8 h/week on collections, about 64 h/month. At a loaded cost of 28 EUR/h, that's 1,792 EUR/month of admin time. She chooses custom automation connected to her ERP (14,000 EUR + 400 EUR/month maintenance). Result: time drops to 20 h/month (560 EUR), saving 1,232 EUR/month, and DSO falls from 60 to 42 days, freeing ~95,000 EUR of one-off cash. The project pays back in ~8 months.
FAQ
Isn't a SaaS enough in every case? No. For simple invoicing, yes, at 39-149 EUR/month. But once you have an in-house ERP, segment-based reminder scales, or complex bank reconciliation, SaaS constrains your rules and custom becomes more profitable beyond ~40,000 EUR/year of admin burden.
How long to go live? A SaaS: 1 to 3 days. Custom automation: 3 to 6 weeks, including a 2-to-5-day initial audit to map your reminder rules and bank flows.
What realistic ROI should I expect? As a 2026 order of magnitude, payback lands between 5 and 9 months for a custom project, driven 80 % by freed time and 20 % by DSO improvement.
Is 2026 e-invoicing handled? Yes, compliant SaaS platforms embed the regulatory format; in custom builds, compliance is part of the spec and must be tested before go-live.
What does 250-500 EUR/month maintenance cover? Keeping connectors alive, rule changes, webhook monitoring, and support. It's the budget line never to forget in a custom project.
Let's scope your project. Tell us your invoice volume, ERP, and reminder rules: we'll frame a SaaS or custom scope with an indicative budget (8,000-18,000 EUR depending on complexity). 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.
