I was in a similar boat a decade ago. I read the FTB documentation (FTB 1031 Sect. E-L) carefully and just accepted it would be subjective criteria test in cou

I was in a similar boat a decade ago. I read the FTB documentation (FTB 1031 Sect. E-L) carefully and just accepted it would be subjective criteria test in court if it ever came down to it. I started keeping immaculate records (motivated by the IRS' substantial presence test or bona fide residence test depending on the year and where the family was in terms of which country it was in — e.g., moving to another). The main points that were relevant — memory serves — were a permanent work contract in the new country and having dissolved housing contracts and similar in CA. My advice: if going abroad, aim to promote your residency status in the new country to "permanent residency" (cf. Green Card, Niederlassungserlaubnis, Niederlassungsbewilligung) over just being permitted either temporary or long-term (cf. Aufenthaltserlaubnis, Kurzaufenthaltsbewilligung). It takes some work to earn permanent residency over the others (e.g., being in good standing, language mastery, and ability to substantively demonstrate financial independence). The idea of earning permanent residency (in a place where it's difficult to earn it) and throwing it away to return to CA suddenly would probably appear preposterous in court in terms of FTB arguing that you're just away from CA temporarily. I kept a US driver license out of convenience in CA. Never was a problem, though I transitioned it to another state where I had family ties and a mailing address hear later. I kept my CA bank account out of practicality. It was the only bank I had dealt with out of about six in rapid succession that was supportive and friendly with my living abroad (e.g., power of attorney, wire transfers without being in-person). Voter registration in CA is fine per Uniformed and Overseas Citizens Absentee Voting Act (UOCAVA). You are entitled your vote; what will differ is whether the state grants you purely federal or also local voting rights. You get federal at a minimum. UOCAVA is a bit hand-wavy with the criteria, so I did transfer my voter registration to the other state where I had the license. For the one year I was half-in California while also being abroad, I still filed taxes accordingly for that year for CA. IIRC, I might have even filed 0 in a CA FTB form for the next year. So: in short, multiple years with "weak" bureaucratic carryover ties in CA without issue, but ultimately transferred all matters aside from bank account to a state with deeper ties (even if living abroad). Never an issue. The real monster, which dates back to the US Civil War, is the need to pay and file taxes when domiciled abroad. You can then add FATCA on top of that as a cherry. The CA FTB is a dream compared to the IRS here. I’ve basically accepted that this situation won’t improve in my lifetime. Maybe my children’s.