I've unfortunately become a payroll tax-witholding specialist.

You're required to withold taxes in the state that work is performed. If you're working from home, that's your work location.

You should get refunded for your CA taxes at the end of the year if they are being withheld.

Like others have said, check with an accountant, I have worked remotely for the past 11 years in NC, for companies in GA, CT and NY, but because I'm 100% remote, I only have to pay NC taxes. None of them ever had an office in NC

I confess I don't know what the laws are then. Presumably you don't pay both your state and CA taxes on your whole salary?

I confess I've never been in the position of being officially completely remote. I certainly don't pay taxes to the state where my company's HQ is but then I'm officially in an office in my state of residence. (And maybe the existence of that office would make a difference even if I weren't actually assigned there.)

Is that something specific to CA?

I've worked remotely for 5 years and have only ever paid state income tax in my home state, not wherever my employer is.

You may want to talk to a CPA or tax specialist. You’re most likely violating your state law as well as overpaying on your taxes.

I've also heard of stories of people getting in trouble for "moving residence" to Incline Village (Nevada) and doing taxes in Nevada while working in CA.