Ask HN: Billing and licensing platform for a Chrome extension?

I'm working on a Chrome extension (https://www.checkbot.io/) that I want to charge for. Can anyone recommend a billing and licensing platform for this? Things I'm looking for: - I want to avoid having to implement or maintain my own server for handling payment details or license verifications as this seems like a lot of work to do right (is it?). - I want the flexibility for payments to be subscription based or one-time purchases plus be able to change the prices of these. - The ability to give out discount codes and affiliation schemes would be a bonus. - I don't want to have to deal with complicated taxes or accountancy. I'm based in the UK. The Chrome Web Store comes with its own payment system but then I cannot easily expand the product to work outside of Chrome later. Also, you can't seem to change the price of subscriptions or offer discount codes. Gumroad looks promising. Would anyone recommend this? They deal with EU taxes for you. When you make a sale, Gumroad give you a license number, the user can enter this into the extension and then a simple REST API call via JavaScript is all that's needed to verify the license is valid so this approach does not require your own server. I'm aware of other services like Paddle, Chargebee, Stripe and SendOwl but it isn't clear to me how I would implement license checking and if I can avoid having to maintain a server. Or maybe the server implementation could be done in a simple way?