Three unusual things about the King's tax bill

King Charles III has revealed a tax bill of £12.9 million, but the payment is far from ordinary. He is not legally required to pay income tax, capital gains tax, or inheritance tax, but does so voluntarily under a Memorandum of Understanding with the government. How the bill was calculated is not disclosed, and the King's personal income, including from the Duchy of Lancaster, is not fully detailed in the report.