The verdict in three sentences
A custom B2B subscription management web app costs EUR 30,000 to 70,000 excluding VAT in Dublin in 2026, with a 12 to 16 week timeline. It replaces manual invoicing of maintenance or rental contracts and automates SEPA direct debits, credit notes and proration. Against Chargebee and its fees of roughly 0.75% of billed revenue, custom pays off once recurring revenue exceeds about EUR 2.5 million a year or your billing rules fall outside the standard.
What the finance director needs to automate
In a recurring services business (lift maintenance, equipment rental, cleaning contracts, managed IT), manual billing is costly: proration errors, missed price reviews, late reminders. With 1,000 customers, an accounts assistant often spends 6 to 8 days a month on it.
| Module | Features | 2026 range (EUR excl. VAT) |
|---|---|---|
| Contract register | Customers, sites, contracts, renewal dates, CPI indexation | 5,000 to 10,500 |
| Billing engine | Billing cycles, proration, discounts, consolidated invoices | 7,000 to 16,000 |
| SEPA direct debits | E-mandates, SEPA files or GoCardless API | 4,000 to 9,500 |
| Credit notes and adjustments | Cancellation, plan changes, disputes | 3,000 to 7,000 |
| Dunning and collections | Email and SMS sequences, late fees | 3,000 to 7,500 |
| Accounting sync | Xero, Sage, QuickBooks, Business Central | 3,500 to 9,500 |
| E-invoicing readiness | Peppol, EN 16931 format | 2,500 to 6,000 |
| Dashboards | MRR, churn, receivables, DSO | 2,000 to 4,000 |
| Total | 30,000 to 70,000 |
Ireland is preparing mandatory B2B e-invoicing in line with the EU ViDA package, with a phased rollout announced from 2028. Building Peppol-ready invoicing now avoids an expensive retrofit.
Custom or Chargebee: the maths
| Criterion | Chargebee (Performance plan) | Custom app |
|---|---|---|
| Setup cost | EUR 5,000 to 15,000 integration | EUR 30,000 to 70,000 excl. VAT |
| Recurring cost | about 0.75% of billed revenue above the plan allowance | EUR 150 to 400/month hosting |
| Maintenance | Included | EUR 5,000 to 12,000/year |
| Specific business rules | Frequent workarounds | Built to fit |
| Annual indexation and price review | Partial | Native |
| Data and code ownership | US vendor | 100% proprietary |
With EUR 3.5 million of billed recurring revenue, 0.75% is EUR 26,250 a year. A EUR 52,000 app plus EUR 9,000 annual maintenance pays back in a little over three years, while fitting your exact rules.
Mini case study
Aoife, finance director of a fire safety maintenance company in Dublin, bills 1,800 customers on annual, quarterly and monthly contracts.
- Today: 7 days a month of manual billing at EUR 360 fully loaded per day, or EUR 30,240 a year, plus 2% of invoices with errors.
- Accepted quote: EUR 55,000 excluding VAT, delivered in 14 weeks.
- After: 1 day a month of review, or EUR 4,320 a year. Savings of EUR 25,920 a year.
- DSO down from 52 to 38 days thanks to SEPA debits, freeing about EUR 100,000 of cash.
Payback comes in a little over two years, excluding the cash flow gain.
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FAQ
How long does development take?
Plan 12 to 16 weeks, including 2 weeks of discovery and 2 weeks to migrate existing contracts. Data migration is often the most underestimated workstream.
Do we need GoCardless for SEPA?
Not necessarily: your bank can process SEPA files directly. GoCardless charges about 1% plus EUR 0.20 per debit, capped, but simplifies mandate management.
Will the app handle e-invoicing?
Yes if it outputs EN 16931 invoices through a Peppol access point. Budget EUR 2,500 to 6,000 for this integration.
Can it handle annual price indexation?
Yes, a CPI-based or fixed percentage increase applies automatically on the contract anniversary, with a simulation before approval.
What if we exceed 3,000 customers?
A well-designed PostgreSQL architecture handles tens of thousands of contracts with no significant extra cost, with hosting under EUR 400 a month.
Let's scope your project. Tell us your customer count, contract types and accounting software, and we will price the app and its data migration. 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.
