Our first time dealing with the remittance basis in HMRC's self assessment carnival of fun! I have a question on how to fill out the self assessment form.

Backstory: My wife is a US citizen, but UK tax resident; She has a chunk of realized capital gains in a US brokerage account that she'll not be remitting to the UK; we want to avoid paying UK capital gains tax on this amount; this is for an earlier tax year when remittance basis was still a thing. I am assuming: she needs to tell HMRC about this gain; she will then go on to claim remittance basis on form SA109, and mail it in (yup, no online submission).

It's the mechanics of this I am confused by. If she confidently ticks Box 28 "If you are making a claim for the remittance basis..." does she need to go on to tell HMRC the actual amount being claimed? If so, where does she input the numbers?

(when we first saw Box 35 "Amount of capital gains you are nominating" we thought ah, this is it, but on reading the notes, this seems to be referring to an amount that she *wants* to be taxed, the opposite of when is intended).

I don’t know the answer but am interested in the responses. There must be plenty of folks who transition from paying tax on a remittance basis to paying tax on a rising basis so hopefully someone will come along with an answer.

If you claim the remittance basis, you still tell HMRC about the foreign capital gains, even if you do not remit them to the UK. You tick the remittance basis box, then report the total foreign gains in the foreign pages, but you only pay UK tax on any amount actually brought into the UK. Box 35 is only for gains you choose to be taxed in the UK, so you normally leave that blank if nothing is remitted. The unremitted gains are disclosed but not taxed. Keep clear records showing the gains stayed outside the UK in case HMRC asks.