@Opus 17 wrote:
I have never heard that any state can make you file a state tax return if you are self-employed and your permanent residence is in another state.
You have now:
See https://www.ftb.ca.gov/forms/2020/2020-1031-publication.pdf
California uses a mandatory market assignment method and single-sales factor apportionment to apportion business income to California. A nonresident may have California sourced income or apportionable business income if receiving income from sales or services sourced to California. Such income includes:
1. Sales of services to the extent that the purchaser of the service receives the benefit of the service in California.
