Taxes are not fun but they need to be handled. Stripe & Billflow can make it easier for you, following are the steps to collect Taxes.
The first thing you need to do is to create a Tax Rate in Stripe. That can be done here. Once you have a tax rate created, you can grab the ID of it, it would look like 'txr_1Gv6cMHSBbxioZ9IxeKTDxSo'.
In order for the tax rate to be applied to a subscription on creation, it must be set as the default tax rate. Grab the ID created and add to the 'Advanced' section of your billing page.
If you want to dynamically pass different tax rates to users based on their region, you can do this with the config options. It will be added to the window setting in an option called 'default_tax_rates'. Setting this on your Plan Picker, Pricing Page, or Checkout form will add the tax rate to your subscription.