Exactly when did he work in MA and when in CA? (The number of days in each state may be significant to the filing requirements.) Was he a resident of MA before the transfer to CA? Is the transfer temporary or permanent? If temporary, how long will the CA employment last? Does he still maintain a residence in MA?
Based on the answers to those questions, he may have to file as:
resident of both states, part-year resident of both states. or resident of MA and non-resident of CA.
He needs to carefully review the residency definitions (both domiciliary and statutory) for both states.
The CA form will be Form 540-NR. CA residency is discussed in FTB Pub. 1031.
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