For UK property disposals which are not your main home, capital gains tax (CGT) will be due on gains which exceed the annual exempt amount (AEA).
Since 6 April 2020, if you’re a UK resident, you have to report and pay any CGT due on the sale of UK residential property within 60 days of the completion date (increase from 30 days in Finance Bill 2022 for property completed on or after 27 October 2021). You do not have to report the gain if there is no tax due. If you’re a non-resident, you must report all sales or disposals of UK property, even if you have no tax to pay or have made a loss.
Currently, you have to use HMRC’s online services to report and pay CGT due on property disposals:
If you’re an agent, you’ll need to use your client’s Capital Gains Tax on UK Property account after requesting authorisation via your Agent Services Account.