The Financial Secretary to the Treasury is a mid-level ministerial post in His Majesty's Treasury. It is nominally the fifth most significant ministerial role within the Treasury after the first lord of the Treasury, the chancellor of the Exchequer, the chief secretary to the Treasury, and the paymaster general. However, the role of First Lord of the Treasury is always held by the prime minister who is not a Treasury minister, and the position of Paymaster General is a sinecure often held by the Minister for the Cabinet Office to allow the holder of that office to draw a government salary. In practice it is, therefore, the third most senior Treasury minister and has attended Cabinet in the past.

His Majesty's Treasury, occasionally referred to as the Exchequer, or more informally the Treasury, is a ministerial department of the Government of the United Kingdom. It is 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.