@ bwagner
If Mac is anything like windows, you can not, if sales tax is turned on it will fill in the sales tax line with a zero amount.

If you remove the sales tax block from the footer of the invoice, QB just adds a line in the description area for sales tax and a zero amount

There is a cheat in windows, bring up the invoice template for a non sales tax invoice, right click on the sales tax title and data blocks and select properties, select font and change the color to white, do that for the borders too - QB will still print the sales tax but it will print white and not be easily seen - assumes you are using white paper of course