Navigation:  Key Concepts > Quick Sale Default

Quick Sale Default is a tax rate which allows Multi-Site customers to make purchases in various stores and always pay the local sales tax.

The actual tax rate will be the same as what you have designated in Maintenance: System Setup: Tax Options: Quick Sale Tax Group.  

You will NOT be able to edit or define this "Quick Sale Default" tax group because it is not visible in the normal tax rate setup.  You may encounter the following screen with Quick Sale Default when editing Customer Categories and Zip Codes.