Tax/VAT support

[zero-master]

EU VAT rates differ per country. So, we'll need some logic to add different rates per state or country.

It can be inbuilt like WHMCS: https://docs.whmcs.com/Tax/VAT

WHMCS does not automatically pull different VAT/TAX rates. So, it will be required to inject VAT rates based on some external API like https://vatapi.com/

Or a plugin integration can be developed (completely outsourcing tax across various jurisdictions) https://www.avalara.com/us/en/index.html