California recently passed the Marketplace Facilitator Act. Effective October 1, 2019, a marketplace facilitator will be considered a seller and retailer for each sale facilitated through its marketplace for nexus purposes.
California requires out-of-state sellers to collect California tax if they have total combined sales of $500,000 or more in a calendar year. The facilitator will add facilitated sales to its own sales when determining whether this threshold is met. A marketplace seller will also count sales made through a marketplace in its total combined sales.
Once a marketplace seller has met the threshold, it should register with the California Department of Taxation and Fee Administration (CDTFA). A marketplace seller will not be responsible for collecting tax on sales made through a marketplace if the facilitator is registered with the state.