How do I know what the default tax code is on the project customer invoice

Summary:

When I create the project draft customer invoice I have the option to view Output Tax Code. However this field doesn't show the actual tax code used to calculate the tax on this draft customer invoice. Is there a way so the default tax code does show? Client has large number of different tax codes, but some use the same tax %. It will be very helpful to understand the default tax code initially used for the tax amount.

Content (please ensure you mask any confidential information):

When I create the project draft customer invoice I have the option to view Output Tax Code. However this field doesn't show the actual tax code used to calculate the tax on this draft customer invoice. Is there a way so the default tax code does show? Client has large number of different tax codes, but some use the same tax %. It will be very helpful to understand the default tax code initially used for the tax amount.