The Love Actually actress, 36, petitioned for bankruptcy at Kingston-Upon-Thames County Court.
Bankruptcy trustees KPMG said the star's "largest creditor" was Her Majesty's Revenue and Customs.
McCutcheon shot to fame at the age of 18 as Tiffany in BBC1 soap EastEnders.
She went on to enjoy a number one hit with the song Perfect Moment and win a Laurence Olivier Award in 2002 for her role as Eliza Doolittle in the stage production of My Fair Lady.
McCutcheon also published a novel, The Mistress in 2009, which was a top 10 bestseller, and starred with Hugh Grant in 2003 film Love Actually.
Last year, she was pictured in Hello! magazine tying-the-knot on the shores of Italy's Lake Como with "best friend" Jack McManus.
McCutcheon, who was the face of Danone Activia yoghurt in its TV adverts, recently filmed an episode of Midsomer Murders.
KPMG'S David Standish, who was appointed joint trustee in bankruptcy of McCutcheon by the Secretary of State on January 24, said: "Ms McCutcheon petitioned for her own bankruptcy at Kingston-Upon-Thames County Court.
"We are now responsible for administering her estate and are in the process of establishing the individual's assets and liabilities, the largest creditor being Her Majesty's Revenue & Customs."
According to her management's website, she is working on a second novel and is in the studio working on new material.