Raymone Bain was responsible for daily operations of The Michael Jackson Co. from 2006 through 2008, including financial, public relations and marketing tasks.
Court documents indicate she should have paid between $200,000 to $400,000.
Under a plea agreement with the government, Bain agreed to pay the back taxes she owes and must file accurate returns covering five years starting in 2004 before her sentencing Aug. 31.
Bain pleaded guilty Wednesday to tax evasion. She could face up to a year in prison and a $100,000 fine for failing to file a federal tax return in 2008, and up to six months in prison and a $5,000 fine for failure to file a District of Columbia tax return in 2008.
The Associated Press contributed to this report.