Duchy of Cornwall
The Duchy of Cornwall (Cornish: Duketh Kernow) is one of two royal duchies in England, the other being the Duchy of Lancaster. The eldest son of the reigning British monarch inherits possession of the duchy and title of Duke of Cornwall at birth or when his parent succeeds to the throne, but may not sell assets for personal benefit and has limited rights and income as a minor.
The current duke is Charles, Prince of Wales. If, and when, the current Prince of Wales accedes to the throne, Prince William will become Duke of Cornwall. When the monarch has no male children, the rights and responsibilities of the duchy revert to the Crown and there is no duke. (The Succession to the Crown Act 2013 does not affect the succession to the duchy, so that if the heir apparent is female she cannot succeed to the duchy.)
The Duchy Council, called the Prince's Council, meets twice a year and is chaired by the duke. The Prince's Council is a non-executive body which provides advice to the duke with regard to the management of the Duchy.[1] The duchy also exercises certain legal rights and privileges across Cornwall and the Isles of Scilly, including some that elsewhere in England belong to the Crown. The duke appoints a number of officials in the county and acts as the port authority for the main harbour of the Isles of Scilly.
The government considers the duchy to be a crown body and therefore exempt from paying corporation tax. The tax exempt status of the duchy has been challenged;[2] and, since 1993, the Duke of Cornwall, the Prince of Wales, has voluntarily paid income tax on the duchy income, less amounts that he considers to be official expenditure.
https://en.wikipedia.org/wiki/Duchy_of_Cornwall