Omid Scobie, author of Finding Freedom, announced that a royal source had confirmed that the money was paid back voluntarily.
Speaking to Harper's BAZAAR U.S., a representative for the couple announced: "This contribution, as originally offered by Prince Harry, has fully covered the necessary renovation costs of Frogmore Cottage, a property of Her Majesty The Queen, and will remain the U.K. residence of The Duke and his family."
Buckingham Palace have also confirmed that the amount was repaid in full to the Sovereign Grant, the British government and tax-payer supported purse that funds the royal family and their endeavours.
"There was never any expectation or request from the Royal Family or the Crown Estate to repay this but they have felt it was important to do so and this is why they proactively offered to repay as soon as the move was announced," the source said.
And while paying the money back in instalments was certainly an option, the source admits that Harry was eager to repay the money in full.
The news comes just days after Harry and Meghan announced that they've signed a deal with Netflix, reportedly worth approximantely AUD $137 million.