If your business is tax exempt, you will need to share that with the seller you are purchasing from by contacting them directly. The seller will be able to inform you what their specific process is for registering as a tax exempt customer and how to provide them with your tax exemption documentation.
It is encouraged that you complete you tax exemption registration with the seller prior to purchasing on your business account, but if you have already made a purchase, you can dispute your invoice with a dispute reason of ‘Buyer Tax Exempt or Incorrect Tax’. Please view the related article for more information.