Financial disclosure forms released by the White House yesterday revealed that the American president is paying 5.625% for a 30-year fixed rate loan for somewhere between $500,000 and $1m he took out in 2005 on his family home in Chicago, according to the Wall Street Journal.

In the US, 30-year fixed rate mortgages are currently priced at 3.65%.

The president is obliged to disclose his financial affairs within a range of figures, rather than detailing actual amounts. Commentators guess his mortgage is around $750,000, meaning that refinancing could save the Obamas around $900 a month.

According to the disclosure forms, the president also sold up to $1 million in short-term Treasury securities in 2012.

Obama’s main source of income is his writing. As president he pulls down an annual salary of $400,000. But in 2012 alone he and earned up to $1 million for a children’s book he wrote – “Of Thee I Sing: A Letter to My Daughters”, and a further $1.1 million in royalties for his books “Dreams from My Father” and “The Audacity of Hope.”

The money earned from the children’s book is donated to fund a scholarship for children of fallen and disabled soldiers.