Hello all,
I use the Stripe Discourse Sub plugin an got my first subscriber. yeah 
Unfortunatly the bill for this subscriber was without tax information, but which is necessary.
I had contact to the stripe support and they said:
I have looked at your Stripe Tax settings, Stripe Tax is configured correctly and automatic tax calculation is enabled.
However, “automatic_tax.enabled” is set to “false” (response text: line 6&7) and thus automatic tax calculation is not applied.
When creating a subscription, you must enable the automatic_tax parameter: Stripe API reference – The subscription object – curl
The stripe support doesn’t know how the discourse plugin works or how to integrate this in the plugin. I have contact to the discourse team and they will have a look into it.
But it will help if more have this issue to made it work.