California residency is defined by an “intent to return to the state of California”. That intent is decided by the FTB not you. Living overseas is particularly

California residency is defined by an “intent to return to the state of California”. That intent is decided by the FTB not you. Living overseas is particularly tricky because they want to see that you’ve established another state in the US with a stronger connection than California. If not, you remain a California resident. Yes, that sounds crazy The state publishes a brochure with something like 40 criteria used to make the determination. Receiving mail inside the state is one indicator https://www.ftb.ca.gov/forms/2020/2020-1031-publication.pdf https://www.ftb.ca.gov/forms/2020/2020-1031-publication.pdf “You can check out any time you like, but you can never leave”