When Tax Rates are added in Both Stock Items and Stock Group, then First Preference will be given to Stock Group and Followed by Stock Item.
When Tax rates are given only at one place either in Stock Items or in Stock Query , then the app will calculate the Tax accord
First Check the tax rate in Stock Item
2. Later Check the tax rate in Stock Group
As you can see now that now , the tax rate in Biz App i.e 14% is taken from Stock Group. So now you can educate the customer that Tax rates is taken Stock Group.