Hi Mike,
Thanks for your update.
Unfortunately, this is not a viable solution for customers within the EU. When a customer wants to place a business order (and the account is not already known in the backend), the checkout must offer the option to choose between a personal or business purchase. If the customer selects a business order, the VAT field should be displayed during checkout. Additionally, there must be an option to validate the VAT number via the VIES system. This is the only correct way to comply with EU regulations regarding ‘VAT reverse charge’ orders and invoices.
The solution you’ve implemented is unfortunately not sufficient. The lack of this functionality is currently the only reason why we’re not migrating all of our webshops to the Shopify platform.