I think I found a solution on QB for Mac:

1. In Preferences > Sales Tax, leave the "customers are charged sales tax" box CHECKED. (I know this doesn't make sense - just go with it.) Make sure "most common sales tax" pull-down is set to "no tax".

2. On the invoice window, in the bottom row of 5 boxes, I have the "%" icon toggled to light grey (as opposed to dark grey). Fiddle with it until it's the lighter color.

3. Below my items on the invoice, there's a pulldown that says "no tax", and next to it says 0.0%. Leave it be, even though next to it there's a line item for 0.00 above the total. Again - just go with it.

4. Now, when I go to preview or print my invoice - voila, no tax!

Why did this work? How did I get it to work? I have no idea. But hopefully it will work for you. Good luck.