As undersecretary and deputy secretary of the Treasury, Summers worked closely with Secretaries Bentsen and Rubin in formulating domestic and international economic policies. He played a key role in designing the United States support program for Mexico in the wake of its 1995 financial crisis and in crafting the international response to the Asian financial crisis of 1997. As deputy secretary, Summers was also instrumental in the introduction of indexed Treasury debt securities, and in the reform of the Internal Revenue Service. When President Clinton appointed Summers as secretary of the Treasury, he called Summers “a critical part of our economic team during the entire life of this administration.”
During Summers’s tenure as secretary of the Treasury, the United States used budget surpluses to repurchase Treasury debt for the first time since the 1920's, and extended the life of the Social Security and Medicare trust funds. Summers led efforts to modernize the financial system, extend financial privacy protections, provide for digital signatures, and insure the viability of the over-the-counter derivatives market. Summers also championed reforms to address corporate tax shelters and predatory lending practices.