Click on your profile icon in the navigation menu.
Click on Settings from the dropdown menu.
Select Billing & Invoices inside your account settings.
Go to the billing information section and click on Company.
Click on the Tax Type button and select your specific category.
Enter your tax number and click Update.
To update this information after purchase:
Click on your profile icon and select Settings.
Click on Billing & Invoices.
Click on Company, enter your new information, and click Update.