It's not just 50. Every locality in Washington state potentially has a different sales tax rate. And, Washington just changed their rules so that the sales tax

It's not just 50. Every locality in Washington state potentially has a different sales tax rate. And, Washington just changed their rules so that the sales tax for instate merchants is not based on where the merchant is located, but where the customer is. So, for every small business that does any business other than through a physical storefront, they need to go based on (at the very minimum) the zipcode. (http://taxrates.dor.wa.gov http://taxrates.dor.wa.gov). And that's just Washington State.