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.
- Click on Rooms on the left.
- Click on the name of the room that you want the tax on upgrade charges to apply.
- Go to the bottom of the bottom of the window and check the applicable tax.
- Click Save when done
Now every time you charge the upgrade it will automatically add the tanning tax to the Register.