Marketplace Fairness – leveling the playing fieldRemote seller sales tax thresholdsBusinesses located in another state, who lack a physical presence in Washington but who make sales to Washington consumers, must follow tax collection laws and may be required to register if they meet either of two thresholds:Threshold one—$100,000 in annual gross retail sales to, or 200 annual transactions with Washington consumersNEW: Beginning October 1, 2018, remote businesses making either $100,000 or more in sale
Source: Marketplace Fairness – leveling the playing field | Washington Department of Revenue