> Merely attending a conference is generally not "CA work" whether or not you take vacation days.
Are you sure? A quote from the CA FTB website [1]:
> A nonresident’s income from California sources includes income from a business, trade, or profession carried on in California. If the nonresident’s business, trade, or profession is carried on both within and outside California and the part outside California is separate and distinct from the part within California, only income from the part conducted within California is California source income.
If you're a salaried employee and you're attending a conference in California and being paid for those days when you're attending, why wouldn't that be considered California source income?
> However, presenting at a conference is work.
You mean if you are getting paid for said presentation? I agree that that one is 100% clearly taxable by California and would probably have been reported to the FTB by the conference organizers. I'm talking about situations where you don't make any additional income beyond your normal salary paid by your employer. If you meant salary received during unpaid presentations too, I'm curious what you think would differentiate that from merely attending the conference for work.
[1] https://www.ftb.ca.gov/individuals/fileRtn/Nonresidents-Part...