In QuickBooks, once your Sales Tax feature is enabled, the system will automatically do the calculations for you. This is to ensure your filings are accurate.
If you are using QuickBooks Online in Ireland, Mexico, Malaysia, Singapore, United Arab Emirates or South Africa, a default set of GST/VAT codes are created for you automatically.
To learn more about sales taxes, the most commonly-used GST/VAT rates, and how you can add the additional tax rates, please check out these articles: