While the particular arrangements for the sharing of data between two Departments is a matter for the Departments concerned, it is my understanding that such sharing is generally governed by a Memorandum of Understanding which sets out the expectations on both sides.
The question of the governance of data-sharing is of great importance. In recognition of this, the Government recently requested my Department to prepare the Heads of a Data-Sharing and Governance Bill, with the following core objectives: to make lawful data-sharing easier by providing a framework that public bodies can use to establish the necessary legal basis; to improve the governance and security of all data-sharing in the public service; and to provide a mechanism that can be used to encourage public bodies to move away from paper documents when dealing with citizens and businesses.