@McCartF --
"Can i ever establish MA residency while working for this CA company?"
Of course you can. People move from one state to another every day.
If you abandon your domicile in CA and establish it in MA, then for tax purposes you become a non-resident of CA and a resident of MA. See Change of Domicile on page 10 of this CA tax publication:
https://www.ftb.ca.gov/forms/2021/2021-1031-publication.pdf
CA taxes non-resident W-2 employees only on CA-source income. W-2 income is sourced where the work is actually (physically) performed. The W-2 income of a CA non-resident who never physically works in CA is not subject to CA income tax.
Your state tax obligations are determined by where you live and work, not by the location of your employer.
Therefore, if you become domiciled in MA and you perform your work only in MA, your employer should withhold MA income tax, not CA income tax. If your employer will not withhold MA income tax for you, you'll have to make quarterly estimated tax payments to MA.
Finally, California law does not require employers to withhold taxes for non-residents who perform no services within California. See FAQ #15 in this CA tax reference:
https://www.ftb.ca.gov/forms/misc/1017.html#1017-12
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
