CA has no dedicated application for safe harbor status, nor does it require that any documentation be submitted with your tax return. But you should be able to prove that you qualify for safe harbor status in the event your return is audited. The key to safe harbor is that you must leave California under an employment-related contract.
You can read all the details of CA's safe harbor rule on pages 4-5 of this CA tax publication:
https://www.ftb.ca.gov/forms/2023/2023-1031-publication.pdf
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
