Christos Vrionides

Hi, I own an overseas property 50/50 with my brother. We we considering either a total sale or me buying him out. There is likely either (1) no capital gain at all after costs or (2) the amount will be below the UK £3000 annual CGT allowance after setting off capital gain paid in the overseas country, and other investment losses during the year. In the two cases (1) and (2) above, do we need to declare the sale/costs/losses to HMRC, or just keep records? Thanks.