Tattoo removal services performed at a tattoo parlor are taxable under the Retailing business and occupation (B&O) tax classification, and the tattoo parlor must collect sales tax.
However, income from tattoo removal services performed by a medical professional at a medical facility is taxable under the Service and Other Activities B&O tax classification, and retail sales tax does not apply.
References
RCW 82.04.050 Sale at retail, retail sale
RCW 82.04.290 Tax on service and other activities
WAC 458-20-224 Service and other business activities