- Choose "Required" or "Optional" in the Magento 2 Tax/VAT switcher in Stores > Customers > Customer Configuration > Name and Address Options.
- Scroll up to "Create New Account Options" and enable "Show VAT Number on Storefront" to turn on Magento 2 VAT validation.
- Finally, go to System > One Step Checkout > Manage Checkout Fields drag and drop VAT filed from disabled fields section to Enabled. Here, you can also remove other unnecessary company fields from Magento 2 checkout. Save changes and flush Magento caches.
Check the website frontend. VAT field is now shown on the checkout page.
→ Create limitless custom checkout fields with the help of the Order Attributes plugin