The heir apparent, Queen Elizabeth II's eldest son, was in India on a nine-day visit before heading to Sri Lanka to open a meeting of leaders from the Commonwealth bloc.
Having paid his taxes while in the Royal Navy, the Prince is entitled to a state pension and it has emerged that he has filled in the required paperwork to access that pension.
But his weekly allowance of 110.15 pounds is intended for a yet to be named old people's charity.
Charles is set to be the oldest-ever person to ascend the British throne.
The prince is currently touring South Asia with his wife Camilla, the Duchess of Cornwall, before flying to the Sri Lankan capital Colombo in the evening.
In Colombo, Charles will attend a reception at the city's British High Commission, where a spokesperson for the prince said there was "likely to be some singing and maybe even a cake".