You will need to contact our Support Team to get your business ID and merchant key. Your VAT ID is something you would get when you register your business not within Shopify.
Please let me know if you have any further questions! I would love to learn more about your business. What type of products do you sell?
Emily | Social Care @ Shopify - Was my reply helpful? Click Like to let me know! - Was your question answered? Mark it as an Accepted Solution - To learn more visit the Shopify Help Center or the Shopify Blog