Bill Gates left the Microsoft board in 2020 as it investigated the billionaire's romantic relationship with a female employee, the Wall Street Journal reported.
The founder and former head of the US technology giant stepped down as board chair in March 2020.
"Microsoft Corp board members decided that Bill Gates needed to step down ... as they pursued an investigation into the billionaire's prior romantic relationship with a female Microsoft employee that was deemed inappropriate," the Journal reported.
This was "an affair almost 20 years ago which ended amicably," a spokeswoman for Gates said.
She added that Gates left Microsoft to focus more on his philanthropic organization, the Bill and Melinda Gates Foundation.
Gates, 65, and wife Melinda, 56, announced their divorce on May 3 after 27 years of marriage.
A committee of the board reviewed the concern about Gates, aided by an outside law firm, a spokesperson for Microsoft said.
The employee, an engineer, claimed in a letter to have had a sexual relationship with Gates over years, the Journal reported.