You'll have to set up the tax code in the Tax Centre first to track VAT/GST. For QBO AE, a set of GST/VAT codes is created for you automatically.
Click Tax, and then Set up tax.
Set up the tax agency details such as the name of your tax agency, any official tax number that has been assigned to your company, your reporting method, how often you file your tax to your tax agency, and whether this tax is meant for sales or purchases, etc....
Once done, you'll see the Tax Centre and a Tax/GST column on your sales and purchase forms.
If you want to add a group tax, here are the steps:
In the Tax Centre, click Add Tax.
Click Group Rate and click Next.
Enter the Tax Code and Description.
Select the Tax Rate and where it applies to Net, Tax or both.
Note: You're unable to edit or delete a group tax.