I've been living in the UK for a few years, paying taxes on the remittance basis and never making any remittances. Earlier this year I was looking into bringing some money over to buy a house and was horrified by the complexity and uncertainty around the taxation of remittances. I ended up paying an accountant to lay out my options, and partly because I was still confused and somewhat skeptical I'm here to check the accountant's verdict against the clearly substantial expertise of people on this board.
My takeaway was that my US-based accounts (one savings account, one brokerage account) are considered "mixed funds", in the sense that they contain both capital and income; remittances from mixed-fund accounts are taxed according to how much of each kind of asset is in the account; if you only bring over part of a mixed-fund account, the different kinds of assets are taxed following a sequence specified by HMRC. (I was told that I could have set things up differently before coming to the UK by creating separate accounts for capital, income, etc, but that it is now too late. Even so, I'd kind of like to know what I could have done.) Anyway, the key thing that I found very surprising (and the main reason why I wanted to check here) is that the accountant said that capital remittances are taxed as *capital gains*. That is, if I had a mixed fund in the US that consisted of a cash gift I had received (say) plus interest on that cash, then when I bring this money to the UK I pay tax on the interest component as if it were income in the UK, and on the capital component as if it were capital gains in the UK, i.e. at 28%. Does this fit with your knowledge of HMRC's rules? What if I had created separate accounts: would remittances from a "capital" account be taxed as capital gains?
The most valuable thing the accountant told me (which should have been clear to me before) was that you can get around all of this by declaring the arising basis during the year in which you bring over money. By his calculations this worked out better than the remittance basis for a year in which I bring over a chunk of money, but then again this is based on the assumption that all of the capital I remit from a mixed fund would be taxed as capital gains.
Thanks in advance for your wisdom -- I hope I've explained the situation clearly.