If you sell your property after 6 April 2020 you must report and pay Capital Gains Tax within 30 days of selling property in the UK.
Capital Gains Tax is a tax on the profit when you sell (or ‘dispose of’) something (an ‘asset’) that’s increased in value.
It’s the gain you make that’s taxed, not the amount of money you receive.
You may have to pay interest and a penalty if you do not report gains on property within the time limit.
You’ll need a Government Gateway user ID and password. If you do not have a user ID, you can create one when you report and pay.
If you sold the property before 6 April 2020, report the gain using the ‘real time’ Capital Gains Tax service or in your next Self Assessment tax return.
For further information; https://www.gov.uk/capital-gains-tax