You need to check the current multi-state taxation rules and the issue of whether or not your activity creates nexus in California. If the work is being done while you are physically in California, or if you are outside of California but do work for clients that are physically in California. California taxes its residents on worldwide income.Once California Residency is established, then California gets every dollar earned worldwide. So read up on California tax residency rules and be aware of when you becomes a tax resident. If you go after July 1st, you may be able to claim to be a Non Resident for 2020 and only pay tax on California source income.
Here is the website for the California Franchise Tax Board. It has the information for California taxes assessed against any business or individual doing business or working as an employee, whether as a full-year resident, a part-year resident, or a nonresident. https://www.ftb.ca.gov.