This paper studies offshore ownership of residential real estate in the United Kingdom and presents three main findings. First, ownership through offshore tax havens is economically significant with a market share above 1.5% overall and around 15% for top-end properties. Second, both tax and disclosure rules shape patterns of offshore ownership, suggesting that taxation and secrecy are important motives for the beneficial owners. Third, lower offshore demand following the Brexit referendum caused prices and vacancy rates to fall, suggesting that offshore ownership has real effects in housing markets by inflating prices and lowering utilization of the housing stock.