If I happen to move my tax residency to another country, do I have to close some of my IB accounts? Does it depend on from where I move?
IB has multiple subsidiaries and assigns each customer to the appropriate one. However, I'm not sure whether the assignment is based on your tax residency or your physical residency. If your account is moved from one subsidiary to another you will be assigned a new account number. IB can transfer all your cash and open positions from one account to the other. You'll have to contact their customer service as this is a manual process, to be done by them.
I´m not certain, how US passport holders are treated. For all others: Well, if you move to UK or EU from outside you will be assigned to a european entity ( UK for UK residents, Ireland, Luxembourg or Hungary for other european residencies - IB`s decision). Under the new EU and ESMA rules there is only ONE residency, as taxwise physical residency is assumed where your wife/family resides, if any doubts remain beyond the 183 days rule.