I was building billing for a company in the US, and I faced complexities, but not the ones mentioned in this article. I didn’t have problems with dates, as we managed quite easily the monthly, quarterly and yearly plans.

We also created a billing based on calendar dates and it was not hard to pro-rate amounts.

I had problems based on locations of my customers. Basically they have different timezones, and billing is based on UTC. This means you have to translate everything based on customers’ timezones.

I also had issue with editing / deleting events for metered billing. When you can erase the past, this is creating a lot of downsides on the accounting side.

This article does not mention the hard things behind compensations, like coupons or credit notes, which is really hard to handle.