Update 7.15.2019: Due to the enactment of Senate Bill 92 in late June, the district tax ordinance is effective April 25, 2019, rather than April 1, 2019. The California Department of Tax and Fee Administration (CDTFA) explains that the date change "eliminates the retroactive effect of AB 147 with regard to the new district use tax collection requirement." See the CDTFA for more details.
Update 4.26.2019: The California Legislature has increased the economic nexus threshold. Retroactively as of April 1, 2019, an out-of-state seller must register with the California Department of Tax and Fee Administration (CDTFA) and collect and remit California sales and use tax if its total combined sales of tangible personal property for delivery in the state exceed $500,000 in the preceding or current calendar year. The 200 transactions threshold is eliminated. In addition, as of October 1, 2019, marketplace facilitators must collect and remit sales tax on all sales made through the marketplace in California. See AB 147 for more details.
After months of deliberation, the California Department of Tax and Fee Administration (CDTFA) has come up with a response to South Dakota v. Wayfair, Inc., the decision by the Supreme Court of the United States that overruled the physical presence rule preventing states from taxing remote sales. California will require out-of-state sellers with a certain amount of economic activity in the state to collect and remit sales tax* starting April 1, 2019.
The significance of this can’t be overstated. Although California is the 30th state to adopt economic nexus in the wake of the Wayfair decision, it’s by far the largest to do so. With a population pushing 40 million and the fifth largest economy in the world, few if any retailers will remain unaffected by this new collection requirement.
Prior to the Supreme Court’s decision in South Dakota v. Wayfair, Inc. (June 21, 2018), states only had the authority to impose a sales tax collection obligation on businesses with a physical presence in the state. In Wayfair, the court found the physical presence constraint to be “unsound and incorrect.” It determined that a business with no physical presence in a state could establish nexus through its “economic and virtual contacts” with the state.