Capital gains tax may be payable on the sale of an asset like a house (usually a second property rather than your main home), shares in companies, valuables like artworks, and sometimes on musical instruments.
From this tax year (April 2020), the deadline for reporting and paying tax on a ‘property’ sale (land or buildings) is now only 30 days from completion of the sale. Previously this information has gone into the next tax return, with the tax due on the relevant 31 January along with income tax. (Information will still need to be included when the tax return is done, to check there is no change to the amount of CGT when the whole year is considered.)
I shall be flagging this to all clients who I know own second properties, and any who have part of their home designated for work only (eg a studio outbuilding). The property market is quiet for now, but the new deadline will be very easy to miss.