First of all make sure that you have:
Defined the appropriate tanning tax in the Setup > Register section.
Added that particular room to the tanning service that will be using that room.
- Added the appropriate charge for upgrade to use that room.
Once the above things are defined, you can now go ahead and select to add taxes to the surcharge (or upgrade) price.
Go to Setup and click on Rooms.
- Click on the name of the room that you want the tax on upgrade charges to apply.
Go to the 2nd tab Options.
In Option 9, check mark the applicable tax.
- Click Save when done.
Now every time you charge the upgrade it will automatically add the tanning tax to the Register.