King Charles will become Britain's first monarch in modern times to reveal his personal tax bill.
His tax payments will be shared on Thursday as a new element in the annual royal financial accounts, with the decision said by Palace sources to have been a personal one by the King.
Buckingham Palace says the move is part of a modernising drive for greater transparency and to "encourage wider understanding of our accountability".
It also follows calls for more openness with regard to royal finances following scandals surrounding Andrew Mountbatten-Windsor.
The move will make public the King's tax payments for the previous year - 2024-25 - and will include tax on his income such as profits from the Duchy of Lancaster, any personal investments and earnings from the King's private estates, such as Sandringham and Balmoral.
A Buckingham Palace spokesman said this was part of a wider drive to be more open with the public.
"To put it simply, we continue to modernise and evolve," they said, with a commitment to an annual publication of the King's taxes.
When he was Prince of Wales, Charles also revealed how much tax he was paying.
Monarchs are not obliged to pay income tax, inheritance tax on what they receive from a previous monarch or capital gains tax - but the King voluntarily pays income tax and capital gains tax on any sale of private assets.
And the total amount paid will be revealed for the first time - including tax on the Duchy of Lancaster's profits, which were about £24m last year.
That property business, including estates in the north of England and property in central London, provides much of the monarch's personal income.
The decision to shift in the direction of more transparency seems to have tuned in to the public mood.
In the wake of the Andrew Mountbatten-Windsor scandals, MPs were among those demanding more openness about the financial dealings of the royals.
Next week's financial report should see a broader account of the royal finances.
"Our aim is to explain all elements of royal finances in a way that further enhances clarity and accessibility," said a Palace spokesman.
The King's tax bill will be published alongside details of the Sovereign Grant, which is the annual public funding for the Royal Household, and covers costs such as staff, the upkeep of buildings and travel on official engagements.
The Sovereign Grant has risen to a record £137.9m, with a temporary increase used to pay for renovations to Buckingham Palace.
Since it was introduced in 2012, the grant has never gone down, but a first reduction is expected to be announced soon as part of a review being carried out by the Treasury, Downing Street and the Royal Household.
MPs will have a chance to debate the Sovereign Grant when legislation comes before Parliament.
Also increasing the scrutiny on royal finances this year will be the Public Accounts Committee, which is going to hold an inquiry into royal property and leases from the Crown Estate.
An initial report from the National Audit Office revealed the daughters of Andrew Mountbatten-Windsor, Princess Beatrice and Princess Eugenie, who are not working royals, had properties in St James's Palace and Kensington Palace.
The rent for their accommodation was paid by the King from his private income.
The Palace says there is already Parliamentary oversight of the Sovereign Grant, but adding personal tax information can "enhance this transparency still further" and in a way "in keeping with our public service priorities".
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