Any disposal of UK land on which a residential property gain arises after 5 April 2020 will be subject to a new reporting and payment regime. Prior to this change the capital gains was notified to HM Revenue and customs via the self assessment system. From 5 April 2020 a return is required to HM Revenue and Customs within 30 days of the completion date. Capital gains tax is also payable within the 30 day deadline.