You can add up to 2 sales taxes to your quotes and
invoices. To do so got to Setup -> System
Values
Once there, go to Tax 1 or Tax 2 tab:
To delete a tax percentage from your list, click on the trash can
To modify a tax percentage, click directly into the value
To add a new tax value, click on "+" symbol
To set a default tax value mark it from the
default column.
TIP: When selecting a default
value, this will be added to all the quotes.