A similar probe was launched into fellow Big Four firm KPMG in February and follows falling corporate tax receipts, which contributed just 7.4% to the total US tax bill, the Wall Street Journal reported.
Almost two-thirds of companies in the US paid no tax in 2000.
E&Y reached a settlement last July over similar allegations, paying $15m (£8.4m) to resolve charges that it failed to comply with rules governing tax shelters, including keeping lists of companies who use them.
It did not admit to any wrongdoing.
A new head of solutions, Aidan Brennan, has been appointed at KPMG UK
Hundreds of jobs are secure after Spectrum Contracting has been sold out of administration to Minstrell Recruitment by FRP Advisory
Cowgill Holloway and Warings Business Advisors have merged, with a range of growth plans in the North West put in place
The Practitioner discusses their timesheet militancy, and reaction to someone playing it fast and loose with the details...