Historically, sales tax collection was based mainly on
physical presence. If you had a store, warehouse, or employees in a state, you were obligated to charge sales tax. But in 2018, the Supreme Court ruling in
South Dakota v. Wayfair, Inc. changed all that. The court decided that states could require online sellers to collect sales tax even if they did not have a physical presence, provided they exceeded certain sales thresholds defined by the respective state.