The deal struck by Skilling's lawyers and federal prosecutors means the former energy-trading executive could be released as early as 2017, the Houston Chronicle said.
The agreement was announced last month. In return for the reduced sentence, Skilling agreed to drop his appeal of his conviction and his claims to $40 million seized by the government.
Skilling has been in a Colorado federal prison for more than six years. He was sentenced to 24 years for wire fraud, insider trading and other charges in the collapse of Enron in 2001.
The Chronicle said the agreement indicated the government had decided it had expended enough resources on the Enron investigation and lengthy litigation.