Charles Schwab requires that you have an account with them 90 days prior to moving overseas. I work with Kyle Davis at Beacon Global Advisors who works with expats like ourselves to figure out what we can do. I recommend reaching out to someone who can help you invest from abroad rather than attempting to do it yourselves.
I moved money from Fidelity and Vanguard to Charles Schwab in anticipation of moving to France. I had conversations with them on the phone during which they assured me that if I opened Schwab accounts in the USA six months before moving to France they would transfer my accounts to Schwab International when I did move. They will not open new accounts for Americans living in France but they will accept established clients living in France into the International branch.
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Marilee Taussig