[the-real-jap]

My company uses Chargebee as the subscription management layer (between stripe and our systems; they perform charging, billing and dunning for us, and also offer us a slick interface to hand out rebates and the like); they are able to at least determine the correct VAT amount for European customers (based on IP/asking the user). It's not free though, but I'm happy we are able to focus on our product instead of those things.