From 6 April 2020, when you sell UK residential property, you need to report via a UK property tax return and pay the capital gains tax within 60 days of completion of the sale.
You may still need to report the disposal on your normal self-assessment return. Where there is joint ownership, each owner needs to make a separate return.
You need the return only when capital gains tax (CGT) is due, using your estimated income for the year for CGT rate purposes.
Due to the tight 60-day deadline, you must set up a capital gains tax UK property account through Government Gateway before proceeding.