Changing your sales taxes / VAT taxes is easy.
FROM THE WEB APP
Step 1: Go to settings > edit company profile
Step 2: Add/Edit your relevant sales taxes
Step 3: Set your default sales tax (Optional)
Step 4: Save (at the bottom of the page)
Step 5: Done!
FROM THE MOBILE APP
This setting can only be changed on the web app at this time. We are working to bring this functionality for the mobile app.