King Charles doesn't have to pay inheritance tax on the Queen's private estate worth more than $750 million

• King Charles has inherited the Duchy of Lancaster estate valued at more than $750 million.
• He will not have to pay inheritance tax on the estate due to a rule approved in 1993.

King Charles will not have to pay inheritance tax on the Duchy of Lancaster estate he inherited from the Queen due to a rule allowing assets to be passed from one sovereign to another.

Charles automatically inherited the estate, the monarch's primary source of income, while his eldest son, Prince William, inherited the Duchy of Cornwall estate - valued at more than $1 billion - from his father.

The new king will avoid inheritance tax on the estate worth more than $750 million due to a rule introduced by the UK government in 1993 to guard against the royal family's assets being wiped out if two monarchs were to die in a short period of time, i News reported.

The provision was first exercised in 2002 when the Queen Mother passed on an estate worth about $80 million to the Queen including a collection of Faberge eggs.

The clause means that, to help protect its assets, members of the royal family do not have to pay the 40% levy on property valued at more than £325,000 ($377,000) that non-royal UK residents do.

The Lancaster estate generated revenue of £24 million ($27 million) last year, its financial records state, and the King is now entitled to its income.

It had assets worth more than £650 million ($754 million) at the end of March this year, the duchy's website states. A law passed in 1702 forbids the monarch from selling any of the assets.

The Queen began voluntarily paying income and capital gains tax on the estate in 1993 and Charles may decide to follow suit.

The Duchy of Lancaster estate, founded in the 13th century, consists of "commercial, agricultural and residential" properties, including a portfolio of financial investments, according to its website.

Its five rural units, or Surveys, cover about 18,000 hectares of land in England and Wales.

The Foreshore Survey covers about 36,000 hectares (one hectare is equal to about two and a half acres) from the river Mersey, on which the city of Liverpool is built, to Barrow-in-Furness in the north of England. It also consists of the Minerals Survey, comprising limestone and sandstone quarries from south Wales to North Yorkshire.

However, most of its income comes from the Urban Survey, which includes extensive commercial property interests in central London such as the Savoy Hotel.

The Balmoral and Sandringham residences are owned by the royal family, while most of the other properties they use including Buckingham Palace and Windsor Castle are part of the Crown Estate.

The Duchy of Lancaster was contacted for comment.