In 1982, California voters approved two ballot measures prohibiting the Legislature or a political subdivision of the State from imposing any tax on or by reason of any transfer occurring by reason of death (i.e., prohibiting an estate tax).
SB 378, however, would enact a California estate, gift, and GST tax (subject to voter approval.) A link to the legislative website with the full text of the bill is below. You can also track the status of the bill through the link.
http://leginfo.legislature.ca.gov/faces/billTextClient.xhtml?bill_id=201920200SB378
If enacted, SB 378 would impose a California estate, gift and generation-skipping transfer tax on transfers by California residents. The effective date for all 3 taxes would be January 1, 2021. The proposed basic exclusion amount is $3,500,000, which is not indexed for inflation. The due dates for filing of returns and payment of tax generally follow the federal rules.
The bill, if passed by the Legislature and signed by Governor Newsom, would have to be ratified by voters in the November 2020 statewide election.