From sole propr., WA LLC, WA partneship or WA Corp.: Each requires an entity certificate filing.
All Internet Business businesses/entities need a business license and an EIN.
Selling/Buying wholesale or retail requires a WA seller's permit.
You can choose to be a(n) :
Seattle Business Tax Registration ( Business License) All businesses including home, online or mobile BUSINESS need a BUSINESS license because they are BUSINESSES.