How I Built a Billing System Without Understanding Billing

Confession: when I started building Energy Backbone’s billing system, I underestimated how complex it would get.

I’m not joking.

I’d been a project manager, a VP, a startup CEO — I know the difference between an invoice and a receipt. But I’d never personally built a billing flow. That was always „someone else’s department.“

Now it was my department. My only department.

Here’s how it went:

Week 1: Naive optimism 😊

„I’ll just connect Mollie and send invoices. How hard can it be?“

Week 2: The rabbit hole 🕳️

„Wait, I need tax calculations? And pro-rata billing for mid-month signups? And currency formatting? And PDF generation? And credit notes for overcharges?“

Week 3: Existential crisis 😰

„Maybe I should just have a human do this manually.“

Week 4: Breakthrough 💡

„Claude, explain Mollie subscription billing to me like I’m a marina operator who just wants to charge people for electricity.“

That last prompt was the turning point.

Instead of trying to learn billing theory, I described my specific use case. Claude walked me through it step by step:

⚡ Meter reading comes in → calculate usage

💰 Usage × rate = amount

📄 Create Mollie invoice with line items

📧 Send to customer automatically

🔄 Handle partial months, rate changes, disputes

Each step was a conversation. „How do I handle this edge case?“ „What if the meter reading is wrong?“ „What about VAT for B2B customers?“

The final system handles:

— Variable usage-based billing

— Monthly subscriptions

— Automatic invoice generation

— Payment tracking and reminders

— Tax calculations for German B2B

Did I become a billing expert? No.

Did I build a billing system that works for real businesses with real money? Yes.

That’s the promise of vibe-coding. You don’t need to be an expert in everything. You need to understand your problem and communicate clearly.

Full story in my article series 👇

https://www.linkedin.com/article/edit/7434497551204253696/

This is part of my 7-part series on vibe-coding. Follow along to see what happens when a non-developer starts building.

This post is part of my series on vibe-coding and building apps without traditional coding skills. All articles in the series →