Welcome to Shopify and congratulations on starting your new business! This is a great question to ask. Your Tax Registration ID and Business Registration ID are provided to you after you apply for a business license and register your business to collect taxes in your local jurisdiction. If you are located in the United States then this would be a good place to start: Apply for licenses and permits - USA.
If you are located elsewhere, try searching for your country + business license in your preferred search engine and take a look at your government website for more information.
It's important to note that starting a business on Shopify is a legitimate business venture and depending on the products you are selling, you may need a range of licenses to ensure your business is in the clear. If you aren't sure what licenses are required for your business, I definitely recommend reaching out to a small business legal professional to assist you in that.
You may also find our Getting Started videos on our youtube channel to be really helpful as you get setup: Learn With Shopify - YouTube. Is there anything else you are working on that I can help with?
Shay | 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