Sales Tax - Due on Internet Sales?

As more businesses make sales or provide services via the Internet, we're often asked wether Internet-based businesses are taxed differently from other businesses. The answer is no.
The following discusses the tax application for internet businesses:

• Items delivered in Washington
  Washington sales tax must be collected on all sales delivered to customers in Washington. Income from these sales is also subject to B&O tax, though items delivered outside of Washington are not subject to B&O.
  
• Items delivered outside of Washington
  When items are delivered to the buyer at a location outside of Washington, the sale is an interstate or foreign sale and exempt from sales tax, as well as B&O tax.
  
• Services performed in Washington
  Providing services in Washington, such as web design, is subject to B&O tax, regardless of the customer's location.

Out-of-state businesses are required to collect Washington sales tax if they have a physical presence in the state of Washington.

For more information, check the Department of Revenue's website.