Harris, who announced last September he was leaving Intuit to pursue an entrepreneurial opportunities, will replace Elon Musk as CEO. Musk, a company founder, will stay on as chairman and oversee product development.
X.com has developed an Internet platform to integrate consumer banking and investment services. The company's lead venture investor is Sequoia Capital. The company plans to launch its public site later this week.
Harris, who was placed at X.com by recruiting firm Heidrick & Struggles, oversaw the relaunch of Intuit's Quicken.com and helped shift its focus to Internet services, which now account for roughly 20 percent of its revenues.
When Harris resigned, Intuit's chairman Bill Campbell took over the daily operations until a successor is found. The company has said it is seeking a new chief executive from outside the company.