The United Kingdom's exit from the European Union, set for March 2019, is less than a year away. The Brexit negotiations include two parts. The first is a withdrawal agreement, to establish the terms of the United Kingdom's departure. London and Brussels expect to finalize this agreement by October. The second part is an agreement on the future trade relationship. The United Kingdom is seeking a comprehensive free trade agreement with the European Union, but such a deal can be signed only after Britain leaves next March because the European Union cannot sign trade agreements with a member state. In recent months, most of the provisions of the withdrawal agreement have been decided, including the future of British contributions to the EU budget and the status of EU citizens living in the United Kingdom and of British citizens living in the European Union. London and Brussels also agreed that Britain will...