[ylere]

My experience has been that there are typically two types of engineers: those who have worked on billing systems before and those who haven't.

I think a lot of the issues arise from the difference between payments and billing [0]. When just starting out and signing up your first customers, you primarily care about collecting a few (recurring) payments - and it's really easy to set that up with Stripe (or even just manually invoicing your first customers).

However, over time, more billing requirements gradually sneak in, such as more complex entitlements, multiple plans, grandfathering, and eventually enterprise/high touch sales customers (where the money is!) who need custom billing cycles, terms, and entitlement provisioning. Since billing is never a technical focus, numerous additions and small hacks accumulate over time, taking engineering resources away from the actual product. Eventually, this turns into an unmanageable mess that can significantly slow down the sales process or limit what you can sell.

The complexity of billing is riddled with hidden pitfalls and edge cases, and it has become even more complex now that most plans include many different limits and usage-based components and that most SaaS companies sell globally. Many later-stage companies have teams of 15+ engineers working solely on billing. I fully agree with the author that, unless it's at the core of your product, no organization should build a billing system themselves (Disclaimer: I'm the CTO of Wingback, a SaaS Billing Platform).

[0] https://www.wingback.com/blog/saas-payment-vs-saas-billing