Ghislaine Maxwell and Jeffrey Epstein shifted totals of $20 million back and forth for a five-year period starting in 2007, according to federal prosecutors.
The revelation comes in a memo from U.S. attorneys in making the argument Maxwell is a flight risk and should be held without bail, CNN reported.
"The fact that she and he would exchange so much money indicates that they had a very close business relationship and that he clearly trusted her with a phenomenal amount of money," former federal prosecutor Duncan Levin told CNN.
"There may be a completely innocent explanation for it, but it definitely is a sinister data point."
Maxwell was arrested Thursday at a New Hampshire estate and has been charged with grooming underage girls for abuse and potential sex trafficking.
Maxwell had argued in a civil lawsuit following Epstein's August death she should have rights to his Virgin Islands estate because she claimed Epstein had vowed to always support her, according to reports.
"They had a very close business relationship and that he clearly trusted her with a phenomenal amount of money," Levin told CNN.