foreign capital gains

I have shares in a US-based mutual fund, which I believe is non-reporting. From reading this forum, I gather that the dividends and capital gains should be reported as offshore income gains (and not capital gains), even though they were re-invested into the fund. I have two more questions: 1) The tax year in the US is the calendar year; can I use the 2022 totals, or do I have to add up the transactions that fell between 6/4/2022 and 5/4/2023? 2) Because I'm a US citizen, I already filed a US tax return that covers these dividends/capital gains. Will I still owe HMRC tax on them?

Hi rmb,
You can use the details to match what you have already submitted and then claim Foreign Tax Credit Relief for the tax paid in the USA to set against the UK tax on the same income.
Thank you.