Washington law (RCW 82.08.0283) provides that sales tax does not apply to sales of “prosthetic devices prescribed, fitted, or furnished for an individual by a person licensed under the laws of this state to prescribe, fit, or furnish prosthetic devices and the components of such prosthetic devices.”

A hearing aid meets the statutory definition of a prosthetic device. Thus, sales of hearing aids, and component parts of hearing aids (such as batteries) are exempt from sales tax when they are prescribed and sold by a medical professional licensed under Washington law to prescribe, fit and sell such items.

However, sales of batteries or other component parts of hearing aids by retail outlets or non-licensed sellers do not qualify for the sales tax exemption for prosthetic devices, and are fully subject to sales tax. This is because retail outlets do not have the type of licensure required by the law to exempt the items.