With reform recommendations from a presidential panel due by July 31, at least one of the proposals would move the United States closer to a model that consists of a tax on income and a type of sales tax commonly known as a value-added tax. Alan Schenk, a tax professor at Wayne State University Law School, says a value-added tax has been proposed in just about every Congress since 1979. The legislation has never gone anywhere, says Schenk, because it lacked White House support.