HM Treasury

Her Majesty's Treasury, occasionally referred to as the Exchequer, or more informally the Treasury, is the department of the Government of the United Kingdom responsible for developing and executing the government's public finance policy and economic policy. The Treasury maintains the Online System for Central Accounting and Reporting, the replacement for the Combined Online Information System, which itemises departmental spending under thousands of category headings, and from which the Whole of Government Accounts annual financial statements are produced.

The possessive adjective in the department's name varies depending upon the gender of the reigning monarch.

Source: Wikipedia