Former media baron Conrad Black must return to federal prison by Sept. 6 under the terms of a judge's sentencing order released Monday, according to a report from the Chicago Tribune.

Black was resentenced on June 24 to 42 months in prison on fraud and obstruction of justice charges, which means he could serve up to 13 more months in prison.

Federal Court Judge Amy St. Eve also ordered him to pay a $125,000 US fine.

Black had already served 29 months in the Coleman federal prison in Florida before the U.S. Supreme Court struck down some of his initial convictions, citing a misuse of the "honest services" provision of the U.S. fraud statute.

His original sentence was for 78 months in prison after multiple convictions on fraud and obstruction of justice charges.

The court agreed to accept the time he has already served, 29 months, as part of his new sentence of 42 months.