1. Do I have to set up a Tax Group even if I only have one tax?
Yes. It may seem redundant but will be needed later anyway if you add more individual taxes.
2. Why don't the taxes calculate when I'm entering invoices?
Taxes will be calculated automatically by the system if they're set up correctly. If they're not calculating right, check the following:
Make sure you have a Tax Group properly set up for the specific tax in question. If you need more help on this, go to Add a Tax Group.
Make sure you have the specific tax included in the Tax Group. It it's not included, then add it. Left-click here to see what this should look like. If you need more help on this, go to Assign a Tax to a Tax Group.
Make sure the Tax Group is assigned to the account and that the specific tax is checked . If it hasn't been checked, then check it. Look at the for the account to see if this has been done correctly. Left-click here to see what this should look like. If you need more help on this, go to Assign a Tax to an Account.
Make sure the product in question has the appropriate tax checked. Go to the specific product and left-click the tab. It should look like this:
Note: If "Charge Tax" is not checked, check it. If you need more help on this, go to Add Taxes to a Product.
Usually, taking care of the steps above will fix the problem. However, if you still have a problem, check to see if the taxes are to be applied based on the location of the customer. This is known as a Point of Sale (or POS) tax. If this is the case, go to How the System Handles Taxes for details.