Do not use the url from the "URL to go to on successful payment/error" fields inside Insales to redirect users after successful/erroneous payment. These are technical addresses, and there will be a 404 error when clicking on them.
Should you have any questions, please do not hesitate to contact your account manager or use our 24/7 Unit.Help chat widget.
VAT is set in your account settings in your Unitpay merchant profile when you fill in the organization information on the /partner/contract page. VAT settings are not passed in Insales itself.