Hi Karen,
If your capital gain is not from a residential property sold after 6 April 2020, you can report your gain, in a Self Assessment Tax return or by using the ‘real time’ Capital Gains Tax Service
Report and pay your Capital Gains Tax
You can use the service to report gains on assets you sold during the tax years 2022 to 2023 & 2023 to 2024.
You can use the capital gains realtime transaction service provided that you report by 31 December in the tax year after you made your gain and pay by 31 January, otherwise the gain must be reported in a tax return.
If you wish to claim for losses, you can do this in writing (include supporting calculations) to H.M. Revenue and Customs Self Assessment BX9 1AS if you do not need to submit a tax return.
If you are required to complete a tax return, the losses are declared on SA108 and should include supporting calculations.
Thank you.