We just launched our website including an online store for selling software licenses. We are based in Austria. Our product is Coati, a source explorer for C/C++: https://www.coati.io/

After speaking to tax accountants and the finance office we decided to go for a reseller. The reseller does the invoicing for you. You just need to do the bookkeeping of the money you get from the reseller. We are using FastSpring. They do monthly subscriptions as well.