Thank you for your kind answer... but for me as an EU customer, it appears that Wise (TransferWise) is regulated by the Bank of Belgium. In fact, this article at Wise, talks about being regulated in UK, EU, & 48 States. This makes it unclear to me where the USD is held in that side of the account. But as an EU customer, it seems that potential Belgium should be listed as where both my Euros and my USD are held (and in fact any other currencies I may choose to have in future), but even writing to them they have not been able to answer me with a direct answer. Will do my best to choose on the FBAR, but nobody seems to know for sure.
