What do i do if i'm in the military and have a vehicle registered in a state i do not reside in?

The vehicle registry is immaterial.  This happens all the time for Military people posted all over the place...but not "at Home". What is important is your Home of record-HOR (or State of Legal Residence-SLR if you legally changed it at some time, with a DD form 2058)

You file taxes for your HOR/SLR state as your state of residence, and only file in the state where you might be posted if you worked off-duty at some civilian job in that "other" state  (or owned a rental property you have income from in the non-resident state).

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CA does occasionally annoy/send out Tax Questions to military people with vehicles bought/registered in CA, even if that person is not a CA HOR/SLR person...and they then have to respond that they are NOT CA Military folks...not sure what documentation is required.

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What is my military state of residence? (intuit.com)