This question probably varies from one state to another, but I had heard that in Wisconsin at least there is supposed to be sales tax charged on services to personal property. Does anyone else have experience with how to find out if this is something that should be done and if it is normally done by piano technicians. I would guess that piano sales would be taxable, but I wasn't sure about piano service.

If you are paying the sales tax to state and local, its your preference to charge customers for it. The tax responsibility is on the seller.