Prince Charles received a ?1 million pay rise from the Duchy of Cornwall last year.
His annual private income from the Duchy estate - which includes the Isles of Scilly - has now risen to more than ?15 million.
Its revenue has doubled in the last five years.
The prince’s annual accounts, to be published at the end of this month, will show his earnings were boosted by rising interest rates as well as property and stock market gains.
Sources said the Duchy estate, set up in 1337, earned ?11 million in what was an ?exceptional? year.
Profits from share dealings are thought to have provided a further ?4 million. Five years ago, the Duchy’s investment portfolio returned income of only ?352,000.
The Duchy’s property assets are now worth ?500 million, while his shares, bonds and other investments are worth ?100 million.
The Clarence House review will also reveal that Charles continues to be the country’s major individual charity benefactor, raising millions for his 16 main charities, including the Prince’s Trust.
And it will show that his office is the equivalent of a mid-sized company with more than 100 staff, of which nearly 30 work for him personally such as chefs, valets and gardeners.
Charles pays the expenses of wife Camilla and those of Princes William and Harry - both of whom are salaried army officers - from his private income.
But taxpayers foot the bill for royal security, maintenance of Clarence House and official trips.
Senior Labour MP Ian Davidson, who sits on the Public Accounts committee, said: “This once again demonstrates the need for there to be closer examination of all of the Prince of Wales’ expenditure.
“Many of us remain concerned that he is able to spend so much money on fripperies while he obtains tax benefits unavailable to the rest of us mere mortals.
“This bumper bonus is the equivalent to winning ?1 million on the lottery for every month of the year.”