The verdict in three sentences
A business ISP in Amsterdam with 3,000 corporate customers (fiber, hosted voice, SD-WAN) that rebills usage and installation fees by hand typically leaks 3% of revenue in billing discrepancies. The CFO has two options in 2026: a SaaS telecom billing platform at 2 to 5 EUR per customer per month, or custom billing and OSS software at 80,000 to 180,000 EUR delivered in 4 to 6 months. Either way, the realistic target is to bring discrepancies down to 0.3% while getting ready for structured e-invoicing.
Why B2B telecom billing goes wrong
A business ISP invoice combines very different items: recurring subscriptions per site, add-ons (static IPs, 4G backup, value-added services), voice usage from CDRs, one-off installation fees, SLA credits to deduct, and prorating for cancellations or relocations. When these flow through exports and spreadsheets, errors pile up: a cancelled line still billed, a fiber installation never invoiced, an expired discount still applied.
| Indicator (2026 order of magnitude) | Semi-manual billing | Automated billing |
|---|---|---|
| Billing discrepancies (over and under) | 3% of revenue | 0.3% target |
| Monthly billing cycle length | 8 to 10 days | 1 to 2 days |
| Missed installation fees | 5 to 8% of installs | Under 0.5% |
| Customer billing complaints per month | 120 to 180 | 20 to 40 |
| FTEs on billing | 3 | 1 to 1.5 |
| Days sales outstanding (DSO) | 55 days | 40 days |
| E-invoicing readiness | To be built | Native via Peppol access point |
Billing SaaS or custom build: the 5-year math
Specialized solutions (SaaS telecom BSS) plug in quickly, but their cost grows with the customer base. A custom build needs upfront investment and a project team on the ISP side, but it matches the real product catalog, integrates directly with OSS (provisioning, network inventory) and does not charge for each extra customer.
| Criterion | SaaS telecom billing | Custom software |
|---|---|---|
| Upfront cost | 20,000 to 50,000 EUR (integration) | 80,000 to 180,000 EUR |
| Recurring cost for 3,000 customers | 6,000 to 15,000 EUR per month | Hosting and maintenance 2,000 to 4,000 EUR per month |
| 5-year cumulative cost | 380,000 to 950,000 EUR | 200,000 to 420,000 EUR |
| Fit with product catalog | Configuration within tool limits | Full |
| OSS and CDR integration | Standard connectors | Custom, real time |
| Time to production | 2 to 4 months | 4 to 6 months |
| Vendor lock-in | High | Code owned by the ISP |
Below 1,000 customers, SaaS is often the right choice. Above 2,000 customers with a complex catalog, custom software becomes clearly cheaper over 5 years. For reference, Kolonell's 11/10/2026 grid prices a complex project of this kind from 7,000,000 FCFA (about 10,670 EUR) up to 15,000,000 FCFA or more (22,870 EUR or more), with a Dakar-based team working alongside the ISP's IT department.
E-invoicing: what changes for an ISP
In the Netherlands, e-invoicing via Peppol is already standard for invoices to central government, and the EU ViDA package is moving all member states toward mandatory structured B2B e-invoicing and digital reporting for cross-border transactions by 2030. For a business ISP, that means producing structured invoices (UBL in the Peppol BIS format), sending them through an access point, and tracking delivery and payment statuses. Well-designed billing software produces these flows natively instead of bolting them on at the end.
Mini case study
Pieter, CFO of a business ISP with 3,000 customers in Amsterdam, bills an average of 450 EUR per customer per month, or 16,200,000 EUR a year. Illustrative scenario: of the 3% in discrepancies, half is unrecovered underbilling, or 243,000 EUR a year. Bringing discrepancies down to 0.3% cuts the loss to 24,300 EUR, recovering about 218,700 EUR a year. The billing team goes from 3 to 1.5 FTEs, freeing about 90,000 EUR of payroll for collections. For custom software at 120,000 EUR plus 36,000 EUR of yearly run cost, payback comes in about 5 months.
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FAQ
How much does billing software for a business ISP cost in 2026?
As SaaS, expect 2 to 5 EUR per customer per month, or 6,000 to 15,000 EUR a month for 3,000 customers. A custom build ranges from 80,000 to 180,000 EUR depending on OSS integrations and the number of product types.
How long does migration take?
Between 4 and 6 months for a custom build, including 4 to 6 weeks of parallel billing with the old system. Parallel runs confirm the gap between both stays under 0.3%.
Is the software ready for e-invoicing?
Yes, when connected to a Peppol access point. It produces UBL invoices and tracks statuses, which already covers Dutch government customers and prepares for EU-wide mandates by 2030.
Can it ingest hosted voice CDRs?
Yes, CDR files are imported and rated automatically, daily or in real time. For 3,000 customers this often means several million lines a month, to be sized during scoping.
What does maintenance cost?
In the Netherlands, maintenance runs 15 to 20% of the build cost per year. At Kolonell, application maintenance ranges from 35,000 to 120,000 FCFA per month (about 50 to 180 EUR), excluding hosting.
Let's scope your project. Share your customer count, product catalog and current OSS tools: we will price the scope, an indicative budget and a migration plan. 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.
