US Secretary of the Treasury Janet Yellen is facing intense scrutiny over a $6 billion mistake made by her department, specifically under the leadership of Deputy Treasury Secretary Adewale Adeyemo's predecessor, Nellie Liang, and then Deputy Secretary Adewale Adeyemo, and Treasury official, Nellie Liang, who was in charge of the department's Office of Financial Research. The error, which occurred in a 2021 tax credit program, resulted in the loss of billions of dollars in revenue for the US government. An investigation has been launched to determine how this mistake occurred and who is accountable for it, putting pressure on Yellen and her team to provide answers and take responsibility for the blunder. The incident has raised questions about the effectiveness of the Treasury Department's oversight and management.