When I worked for a B2B SAAS company, I wired up Stripe with Avalara for calculating sales tax for all our billing statements. It was very unintuitive and was very hard to debug when we encountered issues. On top of it, Avalara's customer support was terrible. It would take at least 3 days for them to get back to our questions. We also looked at some other options outside of Avalara and did not find anything that fit our needs. Due to this our company was losing money literally, since we had to pay that tax ourselves.
What sales tax software do you use for your SAAS business? Did you have a similar experience as mine or was it different?