"There, a nonresident sole proprietor performed all of his services outside of California. However, some of his customers were located in California. Is that enough for the poor guy to attract California tax liability? The California taxing authorities said he was operating a "unitary" business. Therefore, his tiny business was subject to California's apportionment rules."
"The California Franchise Tax Board matched income records showing that he collected $40,000 of income from California companies. Not surprisingly, Bindley did not file a California tax return. That meant California’s statute of limitations would never start to run."
So should out-of-state freelancers avoid taking on any CA clients?